Last data update: May 06, 2024. (Total: 46732 publications since 2009)
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COVID-19 mortality and progress toward vaccinating older adults - World Health Organization, Worldwide, 2020-2022
Wong MK , Brooks DJ , Ikejezie J , Gacic-Dobo M , Dumolard L , Nedelec Y , Steulet C , Kassamali Z , Acma A , Ajong BN , Adele S , Allan M , Cohen HA , Awofisayo-Okuyelu A , Campbell F , Cristea V , De Barros S , Edward NV , Waeber Arec , Guinko TN , Laurenson-Schafer H , Mahran M , Carrera RM , Mesfin S , Meyer E , Miglietta A , Mirembe BB , Mitri M , Nezu IH , Ngai S , Ejoh OO , Parikh SR , Peron E , Sklenovská N , Stoitsova S , Shimizu K , Togami E , Jin YW , Pavlin BI , Novak RT , Le Polain O , Fuller JA , Mahamud AR , Lindstrand A , Hersh BS , O'Brien K , Van Kerkhove MD . MMWR Morb Mortal Wkly Rep 2023 72 (5) 113-118 After the emergence of SARS-CoV-2 in late 2019, transmission expanded globally, and on January 30, 2020, COVID-19 was declared a public health emergency of international concern.* Analysis of the early Wuhan, China outbreak (1), subsequently confirmed by multiple other studies (2,3), found that 80% of deaths occurred among persons aged ≥60 years. In anticipation of the time needed for the global vaccine supply to meet all needs, the World Health Organization (WHO) published the Strategic Advisory Group of Experts on Immunization (SAGE) Values Framework and a roadmap for prioritizing use of COVID-19 vaccines in late 2020 (4,5), followed by a strategy brief to outline urgent actions in October 2021.(†) WHO described the general principles, objectives, and priorities needed to support country planning of vaccine rollout to minimize severe disease and death. A July 2022 update to the strategy brief(§) prioritized vaccination of populations at increased risk, including older adults,(¶) with the goal of 100% coverage with a complete COVID-19 vaccination series** for at-risk populations. Using available public data on COVID-19 mortality (reported deaths and model estimates) for 2020 and 2021 and the most recent reported COVID-19 vaccination coverage data from WHO, investigators performed descriptive analyses to examine age-specific mortality and global vaccination rollout among older adults (as defined by each country), stratified by country World Bank income status. Data quality and COVID-19 death reporting frequency varied by data source; however, persons aged ≥60 years accounted for >80% of the overall COVID-19 mortality across all income groups, with upper- and lower-middle-income countries accounting for 80% of the overall estimated excess mortality. Effective COVID-19 vaccines were authorized for use in December 2020, with global supply scaled up sufficiently to meet country needs by late 2021 (6). COVID-19 vaccines are safe and highly effective in reducing severe COVID-19, hospitalizations, and mortality (7,8); nevertheless, country-reported median completed primary series coverage among adults aged ≥60 years only reached 76% by the end of 2022, substantially below the WHO goal, especially in middle- and low-income countries. Increased efforts are needed to increase primary series and booster dose coverage among all older adults as recommended by WHO and national health authorities. |
Progress toward poliomyelitis eradication - Pakistan, January 2018-September 2019
Hsu CH , Kader M , Mahamud A , Bullard K , Jorba J , Agbor J , Safi MM , Jafari HS , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2019 68 (45) 1029-1033 Afghanistan and Pakistan are the only countries that continue to confirm ongoing wild poliovirus type 1 (WPV1) transmission (1). During January 2018-September 2019 the number of WPV1 cases in Pakistan increased, compared with the number during the previous 4 years. This report updates previous reports on Pakistan's polio eradication activities, progress, and challenges (2,3). In 2018, Pakistan reported 12 WPV1 cases, a 50% increase from eight cases in 2017, and a 31% increase in the proportion of WPV1-positive sites under environmental surveillance (i.e., sampling of sewage to detect poliovirus). As of November 7, 2019, 80 WPV1 cases had been reported, compared with eight cases by the same time in 2018. An intensive schedule of supplementary immunization activities (SIAs)* implemented by community health workers in the core reservoirs (i.e., Karachi, Peshawar, and Quetta) where WPV1 circulation has never been interrupted, and by mobile teams, has failed to interrupt WPV1 transmission in core reservoirs and prevent WPV1 resurgence in nonreservoir areas. Sewage samples have indicated wide WPV1 transmission in nonreservoir areas in other districts and provinces. Vaccine refusals, chronically missed children, community campaign fatigue, and poor vaccination management and implementation have exacerbated the situation. To overcome challenges to vaccinating children who are chronically missed in SIAs and to attain country and global polio eradication goals, substantial changes are needed in Pakistan's polio eradication program, including continuing cross-border coordination with Afghanistan, gaining community trust, conducting high-quality vaccination campaigns, improving oversight of field activities, and improving managerial processes to unify eradication efforts. |
Progress toward poliomyelitis eradication - Pakistan, January 2017-September 2018
Hsu C , Mahamud A , Safdar M , Nikulin J , Jorba J , Bullard K , Agbor J , Kader M , Sharif S , Ahmed J , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2018 67 (44) 1242-1245 Among the three wild poliovirus (WPV) serotypes, only WPV type 1 (WPV1) has been reported in polio cases or detected from environmental surveillance globally since 2012. Pakistan remains one of only three countries worldwide (the others are Afghanistan and Nigeria) that has never had interrupted WPV1 transmission. This report documents Pakistan's activities and progress toward polio eradication during January 2017-September 2018 and updates previous reports (1,2). In 2017, Pakistan reported eight WPV1 cases, a 60% decrease from 20 cases in 2016. As of September 18, 2018, four cases had been reported, compared with five cases at that time in 2017. Nonetheless, in 2018, WPV1 continues to be isolated regularly from environmental surveillance sites, primarily in the core reservoir areas of Karachi, Quetta, and Peshawar, signifying persistent transmission. Strategies to increase childhood immunity have included an intense schedule of supplemental immunization activities (SIAs), expanding and refining deployment of community-based vaccination implemented by community health workers recruited from the local community in reservoir areas, and strategic placement of permanent transit points where vaccination is provided to mobile populations. Interruption of WPV1 transmission will require further programmatic improvements throughout the country with a focus on specific underperforming subdistricts in reservoir areas. |
Fractional-dose inactivated poliovirus vaccine campaign - Sindh Province, Pakistan, 2016
Pervaiz A , Mbaeyi C , Baig MA , Burman A , Ahmed JA , Akter S , Jatoi FA , Mahamud A , Asghar RJ , Azam N , Shah MN , Laghari MA , Soomro K , Wadood MZ , Ehrhardt D , Safdar RM , Farag N . MMWR Morb Mortal Wkly Rep 2017 66 (47) 1295-1299 Following the declaration of eradication of wild poliovirus (WPV) type 2 in September 2015, trivalent oral poliovirus vaccine (tOPV) was withdrawn globally to reduce the risk for type 2 vaccine-derived poliovirus (VDPV2) transmission; all countries implemented a synchronized switch to bivalent OPV (type 1 and 3) in April 2016 (1,2). Any isolation of VDPV2 after the switch is to be treated as a potential public health emergency and might indicate the need for supplementary immunization activities (3,4). On August 9, 2016, VDPV2 was isolated from a sewage sample taken from an environmental surveillance site in Hyderabad, Sindh province, Pakistan. Possible vaccination activities in response to VDPV2 isolation include the use of injectable inactivated polio vaccine (IPV), which poses no risk for vaccine-derived poliovirus transmission. Fractional-dose, intradermal IPV (fIPV), one fifth of the standard intramuscular dose, has been developed to more efficiently manage limited IPV supplies. fIPV has been shown in some studies to be noninferior to full-dose IPV (5,6) and was used successfully in response to a similar detection of a single VDPV2 isolate from sewage in India (7). Injectable fIPV was used for response activities in Hyderabad and three neighboring districts. This report describes the findings of an assessment of preparatory activities and subsequent implementation of the fIPV campaign. Despite achieving high coverage (>80%), several operational challenges were noted. The lessons learned from this campaign could help to guide the planning and implementation of future fIPV vaccination activities. |
Progress toward poliomyelitis eradication - Pakistan, January 2016-September 2017
Elhamidi Y , Mahamud A , Safdar M , Al Tamimi W , Jorba J , Mbaeyi C , Hsu CH , Wadood Z , Sharif S , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2017 66 (46) 1276-1280 In 1988, the World Health Assembly launched the Global Polio Eradication Initiative. Among the three wild poliovirus serotypes, only wild poliovirus (WPV) type 1 (WPV1) has been detected since 2012. Since 2014, Pakistan, Afghanistan, and Nigeria remain the only countries with continuing endemic WPV1 transmission. This report describes activities conducted and progress made toward the eradication of poliovirus in Pakistan during January 2016-July 2017 and provides an update to previous reports (1,2). In 2016, Pakistan reported 20 WPV1 cases, a 63% decrease compared with 54 cases in 2015 (3). As of September 25, 2017, five WPV1 cases have been reported in 2017, representing a 69% decline compared with 16 cases reported during the same period in 2016 (Figure 1). During January-September 2017, WPV1 was detected in 72 of 468 (15%) environmental samples collected, compared with 36 of 348 (9%) samples collected during the same period in 2016. WPV1 was detected in environmental samples in areas where no polio cases are being reported, which indicates that WPV1 transmission is continuing in some high-risk areas. Interruption of WPV transmission in Pakistan requires maintaining focus on reaching missed children (particularly among mobile populations), continuing community-based vaccination, implementing the 2017-2018 National Emergency Action Plan (4), and improving routine immunization services. |
Response to a large polio outbreak in a setting of conflict - Middle East, 2013-2015
Mbaeyi C , Ryan MJ , Smith P , Mahamud A , Farag N , Haithami S , Sharaf M , Jorba JC , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2017 66 (8) 227-231 As the world advances toward the eradication of polio, outbreaks of wild poliovirus (WPV) in polio-free regions pose a substantial risk to the timeline for global eradication. Countries and regions experiencing active conflict, chronic insecurity, and large-scale displacement of persons are particularly vulnerable to outbreaks because of the disruption of health care and immunization services. A polio outbreak occurred in the Middle East, beginning in Syria in 2013 with subsequent spread to Iraq. The outbreak occurred 2 years after the onset of the Syrian civil war, resulted in 38 cases, and was the first time WPV was detected in Syria in approximately a decade. The national governments of eight countries designated the outbreak a public health emergency and collaborated with partners in the Global Polio Eradication Initiative (GPEI) to develop a multiphase outbreak response plan focused on improving the quality of acute flaccid paralysis (AFP) surveillance and administering polio vaccines to >27 million children during multiple rounds of supplementary immunization activities (SIAs). Successful implementation of the response plan led to containment and interruption of the outbreak within 6 months of its identification. The concerted approach adopted in response to this outbreak could serve as a model for responding to polio outbreaks in settings of conflict and political instability. |
Progress toward poliomyelitis eradication - Pakistan, January 2015-September 2016
Hsu CH , Mahamud A , Safdar RM , Ahmed J , Jorba J , Sharif S , Farag N , Martinez M , Tangermann RH , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2016 65 (46) 1295-1299 Pakistan, Afghanistan, and Nigeria remain the only countries where endemic wild poliovirus type 1 (WPV1) transmission continues. This report describes the activities, challenges, and progress toward polio eradication in Pakistan during January 2015-September 2016 and updates previous reports. In 2015, a total of 54 WPV1 cases were reported in Pakistan, an 82% decrease from 2014. In 2016, 15 WPV1 cases had been reported as of November 1, representing a 61% decrease compared with the 38 cases reported during the same period in 2015. Among the 15 WPV1 cases reported in 2016, children aged <36 months accounted for 13 cases; four of those children had received only a single dose of oral poliovirus vaccine (OPV). Seven of the 15 WPV1 cases occurred in the province of Khyber Pakhtunkhwa (KP), five in Sindh, two in the Federally Administered Tribal Areas (FATA), and one in Balochistan. During January-September 2016, WPV1 was detected in 9% (36 of 384) of environmental samples collected, compared with 19% (69 of 354) of samples collected during the same period in 2015. Rigorous implementation of the 2015-2016 National Emergency Action Plan (NEAP), coordinated by the National Emergency Operations Center (EOC), has resulted in a substantial decrease in overall WPV1 circulation compared with the previous year. However, detection of WPV1 cases in high-risk areas and the detection of WPV1 in environmental samples from geographic areas where no polio cases are identified highlight the need to continue to improve the quality of supplemental immunization activities (SIAs), immunization campaigns focused on vaccinating children with OPV outside of routine immunization services, and surveillance for acute flaccid paralysis (AFP). Continuation and refinement of successful program strategies, as outlined in the new 2016-2017 NEAP, with particular focus on identifying children missed by vaccination, community-based vaccination, and rapid response to virus identification are needed to stop WPV transmission. |
Polio outbreak investigation and response in Somalia, 2013
Kamadjeu R , Mahamud A , Webeck J , Baranyikwa MT , Chatterjee A , Bile YN , Birungi J , Mbaeyi C , Mulugeta A . J Infect Dis 2014 210 Suppl 1 S181-6 BACKGROUND: For >2 decades, conflicts and recurrent natural disasters have maintained Somalia in a chronic humanitarian crisis. For nearly 5 years, 1 million children <10 years have not had access to lifesaving health services, including vaccination, resulting in the accumulation by 2012 of the largest geographically concentrated cohort of unvaccinated children in the world. This article reviews the epidemiology, risk, and program response to what is now known as the 2013 wild poliovirus (WPV) outbreak in Somalia and highlights the challenges that the program will face in making Somalia free of polio once again. METHODS: A case of acute flaccid paralysis (AFP) was defined as a child <15 years of age with sudden onset of fever and paralysis. Polio cases were defined as AFP cases with stool specimens positive for WPV. RESULTS: From 9 May to 31 December 2013, 189 cases of WPV type 1 (WPV1) were reported from 46 districts of Somalia; 42% were from Banadir region (Mogadishu), 60% were males, and 93% were <5 years of age. All Somalian polio cases belonged to cluster N5A, which is known to have been circulating in northern Nigeria since 2011. In response to the outbreak, 8 supplementary immunization activities were conducted with oral polio vaccine (OPV; trivalent OPV was used initially, followed subsequently by bivalent OPV) targeting various age groups, including children aged <5 years, children aged <10 years, and individuals of any age. CONCLUSIONS: The current polio outbreak erupted after a polio-free period of >6 years (the last case was reported in March 2007). Somalia interrupted indigenous WPV transmission in 2002, was removed from the list of polio-endemic countries a year later, and has since demonstrated its ability to control polio outbreaks resulting from importation. This outbreak reiterates that the threat of large polio outbreaks resulting from WPV importation will remain constant unless polio transmission is interrupted in the remaining polio-endemic countries. |
Progress toward polio eradication-Somalia, 1998-2013
Mbaeyi C , Kamadjeu R , Mahamud A , Webeck J , Ehrhardt D , Mulugeta A . J Infect Dis 2014 210 Suppl 1 S173-80 Since the 1988 resolution of the World Health Assembly to eradicate polio, significant progress has been made toward achieving this goal, with the result that only Afghanistan, Nigeria, and Pakistan have never successfully interrupted endemic transmission of wild poliovirus. However, one of the greatest challenges of the Global Polio Eradication Initiative has been that of maintaining the polio-free status of countries in unstable regions with weak healthcare infrastructure, a challenge exemplified by Somalia, a country in the Horn of Africa region. Somalia interrupted indigenous transmission of wild poliovirus in 2002, 4 years after the country established its national polio eradication program. But political instability and protracted armed conflict, with significant disruption of the healthcare system, have left Somalia vulnerable to 2 imported outbreaks of wild poliovirus. The first occurred during 2005-2007, resulting in >200 cases of paralytic polio, whereas the second, which began in 2013, is currently ongoing. Despite immense challenges, the country has a sensitive surveillance system that has facilitated prompt detection of outbreaks, but its weak routine immunization system means that supplementary immunization activities constitute the primary strategy for reaching children with polio vaccines. Conducting vaccination campaigns in a setting of conflict has been at times hazardous, but the country's polio program has demonstrated resilience in overcoming many obstacles to ensure that children receive lifesaving polio vaccines. Regaining and maintaining Somalia's polio-free status will depend on finding innovative and lasting solutions to the challenge of administering vaccines in a setting of ongoing conflict and instability. |
Effectiveness of oral polio vaccination against paralytic poliomyelitis: a matched case-control study in Somalia
Mahamud A , Kamadjeu R , Webeck J , Mbaeyi C , Baranyikwa MT , Birungi J , Nurbile Y , Ehrhardt D , Shukla H , Chatterjee A , Mulugeta A . J Infect Dis 2014 210 Suppl 1 S187-93 BACKGROUND: After the last case of type 1 wild poliovirus (WPV1) was reported in 2007, Somalia experienced another outbreak of WPV1 (189 cases) in 2013. METHODS: We conducted a retrospective, matched case-control study to evaluate the vaccine effectiveness (VE) of oral polio vaccine (OPV). We retrieved information from the Somalia Surveillance Database. A case was defined as any case of acute flaccid paralysis (AFP) with virological confirmation of WPV1. We selected two groups of controls for each case: non-polio AFP cases ("NPAFP controls") matched to WPV1 cases by age, date of onset of paralysis and region; and asymptomatic "neighborhood controls," matched by age. Using conditional logistic regression, we estimated the VE of OPV as (1- odds ratio) x100. RESULT: We matched 99 WPV cases with 99 NPAFP controls and 134 WPV1 cases with 268 neighborhood controls. Using NPAFP controls, the overall VE was 70% (95% confidence interval [CI], 37-86), 59% (2-83) among 1-3 dose recipients, 77% (95% CI, 46-91) among ≥4 dose recipients. In neighborhood controls, the overall VE was 95% (95% CI, 84-98), 92% (72-98) among 1-3 dose recipients, and 97% (89-99) among ≥4 dose recipients. When the analysis was limited to cases and controls ≤24 months old, the overall VE in NPAFP and neighborhood controls was 95% (95% CI, 65-99) and 97% (95% CI, 76-100), respectively. CONCLUSIONS: Among individuals who were fully vaccinated with OPV, vaccination was effective at preventing WPV1 in Somalia. |
Measles outbreak response among adolescent and adult Somali refugees displaced by famine in Kenya and Ethiopia, 2011
Navarro-Colorado C , Mahamud A , Burton A , Haskew C , Maina GK , Wagacha JB , Ahmed JA , Shetty S , Cookson S , Goodson JL , Schilperoord M , Spiegel P . J Infect Dis 2014 210 (12) 1863-70 BACKGROUND: The refugee complexes of Dadaab, Kenya, and Dollo-Ado, Ethiopia, experienced measles outbreaks during June-November 2011, following a large influx of refugees from Somalia. METHODS: Line-lists from health facilities were used to describe the outbreak in terms of age, sex, vaccination status, arrival date, attack rates (ARs), and case fatality ratios (CFRs) for each camp. Vaccination data and coverage surveys were reviewed. RESULTS: In Dadaab, 1370 measles cases and 32 deaths (CFR, 2.3%) were reported. A total of 821 cases (60.1%) were aged ≥15 years, 906 (82.1%) arrived to the camps in 2011, and 1027 (79.6%) were unvaccinated. Camp-specific ARs ranged from 212 to 506 cases per 100 000 people. In Dollo-Ado, 407 cases and 23 deaths (CFR, 5.7%) were reported. Adults aged ≥15 years represented 178 cases (43.7%) and 6 deaths (26.0%). Camp-specific ARs ranged from 21 to 1100 cases per 100 000 people. Immunization activities that were part of the outbreak responses initially targeted children aged 6 months to 14 years and were later expanded to include individuals up to 30 years of age. CONCLUSIONS: The target age group for outbreak response-associated immunization activities at the start of the outbreaks was inconsistent with the numbers of cases among unvaccinated adolescents and adults in the new population. In displacement of populations from areas affected by measles outbreaks, health authorities should consider vaccinating adults in routine and outbreak response activities. |
Varicella zoster virus in American Samoa: seroprevalence and predictive value of varicella disease history in elementary and college students
Mahamud A , Leung J , Masunu-Faleafaga Y , Teshale E , Williams R , Dulski T , Thieme M , Garcia P , Schmid DS , Bialek SR . Epidemiol Infect 2014 142 (5) 1002-7 The epidemiology of varicella is believed to differ between temperate and tropical countries. We conducted a varicella seroprevalence study in elementary and college students in the US territory of American Samoa before introduction of a routine varicella vaccination programme. Sera from 515 elementary and 208 college students were tested for the presence of varicella-zoster virus (VZV) IgG antibodies. VZV seroprevalence increased with age from 76.0% in the 4-6 years group to 97.7% in those aged 23 years. Reported history of varicella disease for elementary students was significantly associated with VZV seropositivity. The positive and negative predictive values of varicella disease history were 93.4% and 36.4%, respectively, in elementary students and 97.6% and 3.0%, respectively, in college students. VZV seroprevalence in this Pacific island appears to be similar to that in temperate countries and suggests endemic VZV circulation. |
Risk factors for measles mortality among hospitalized Somali refugees displaced by famine, Kenya, 2011
Mahamud A , Burton A , Hassan M , Ahmed JA , Wagacha JB , Spiegel P , Haskew C , Eidex RB , Shetty S , Cookson S , Navarro-Colorado C , Goodson JL . Clin Infect Dis 2013 57 (8) e160-6 BACKGROUND: Measles among displaced, malnourished populations can result in a high case fatality ratio (CFR). In 2011, a large measles outbreak occurred in Dadaab, Kenya among refugees fleeing famine and conflict in Somalia. The aim of this study was to identify predictors of measles deaths among hospitalized patients during the outbreak. METHODS: A retrospective cohort study design was used to investigate measles mortality among hospitalized measles patients with a date of rash onset during June 6-September 10, 2011. Data were abstracted from medical records and a measles case was defined as an illness with fever, maculopapular rash, and either cough, coryza or conjunctivitis. Vaccination status was determined by patient or parental recall. Independent predictors of mortality were identified using logistic regression. RESULTS: Of 388 hospitalized measles patients, 188 (49%) were from hospital X, 70 (18%) from hospital Y, and 130 (34%) from hospital Z; median age was 22 years, 192 (50%) were 15-29 years of age, and 22 (6%) were vaccinated. The mean number of days from rash onset to hospitalization varied by hospital (hospital X=5, hospital Y=3, hospital Z=6 [p<0.0001]). Independent risk factors for measles mortality were neurological complications (OR=12.8, 95% CI =3.1-52.4), acute malnutrition (OR=7.6, 95% CI=1.3-44.3), and admission to hospital Z (OR=4.2, 95% CI=1.3-13.2). CONCLUSIONS: Among Somali refugees, in addition to timely vaccination at border crossing points, early detection and treatment of acute malnutrition, and proper management of measles cases may reduce measles mortality. |
Seroprevalence of measles, mumps and rubella among children in American Samoa, 2011, and progress towards West Pacific Region goals of elimination
Mahamud A , Masunu-Faleafaga Y , Walls L , Williams N , Garcia P , Teshale E , Williams R , Dulski T , Bellini WJ , Kutty PK . Vaccine 2013 31 (36) 3683-7 INTRODUCTION: In line with the global goals for measles elimination, countries in the West Pacific Region (WPR) have set a goal to eliminate measles by 2012. Due to its contagiousness, high population immunity is needed for achieving and documenting measles elimination. We assessed population immunity to measles, mumps and rubella among first grade children in American Samoa (AS) through a seroprevalance study. METHODS: Using commercial indirect enzyme-linked immunosorbant IgG assays (Wampole Laboratories, Cranbury, NJ) we determined IgG antibodies against the measles, mumps, and rubella (MMR) viruses in sera collected from first grade students in AS in April-May 2011. Vaccination status was retrieved from the immunization cards. Factors associated with seropositivity of measles, mumps, and rubella were analyzed separately. RESULT: Among 509 first grade students, measles, mumps, and rubella seroprevalence were 92%, 90%, and 93%, respectively. The proportions of first grade students with documented one or two doses of MMR vaccine were 93% and 84%, respectively. The vaccination status of 6% of the first graders was unknown and 1% was unvaccinated. Receiving two-doses of MMR vaccines was associated with high measles and mumps seropositivity (p<0.01). CONCLUSION: The high measles seroprevalence among children shows the progress by American Samoa towards measles elimination. Achieving and maintaining high two-dose MMR vaccine coverage in all age groups will aid in attaining the measles elimination status and prevent transmission of measles from potential imported measles cases from other countries. |
Immunity to hepatitis B virus infection two decades after implementation of universal infant hepatitis B vaccination: the association of detectable residual antibody and response to a single hepatitis B vaccine challenge dose
Spradling PR , Xing J , Williams R , Masunu-Faleafaga Y , Dulski T , Mahamud A , Drobeniuc J , Teshale EH . Clin Vaccine Immunol 2013 20 (4) 559-61 Most persons who receive hepatitis B vaccine during infancy will have a level of antibody to hepatitis B surface antigen (anti-HBs) <10 IU/L if measured 10-15 years later; however, most will demonstrate immune memory by an anamnestic response to a vaccine challenge dose. To determine whether there was a difference in anamnestic response among college students vaccinated during infancy, we compared anti-HBs levels after a dose of Engerix-B 20 mcg between those with a residual anti-HBs level of 0 IU/L versus those with a level of 1-9 IU/L. Anti-HBs was measured before (baseline) and two weeks after a challenge dose; response was defined as a level ≥10 IU/L after the dose among those <10 IU/L at baseline. Among 153 students who completed the study, 130 (85%) had an anti-HBs level <10 IU/L at baseline; 72 had a level of 0 IU/L and 58 had a level ranging from 1 to 9 IU/L. Students with a level from 1-9 IU/L were more likely to respond to the challenge dose compared to those with a baseline anti-HBs level of 0 IU/L (83% versus 50%; p<0.001). The presence of any detectable anti-HBs among persons vaccinated in the remote past may indicate the persistence of immune memory. |
Epidemiology of a mumps outbreak in a highly vaccinated island population and use of a third dose of measles-mumps-rubella vaccine for outbreak control- Guam 2009-2010
Nelson GE , Aguon A , Valencia E , Oliva R , Guerrero ML , Reyes R , Lizama A , Diras D , Mathew A , Camacho EJ , Monforte MN , Chen TH , Mahamud A , Kutty PK , Hickman C , Bellini WJ , Seward JF , Gallagher K , Fiebelkorn AP . Pediatr Infect Dis J 2012 32 (4) 374-80 BACKGROUND: Despite high two-dose measles-mumps-rubella (MMR) vaccine coverage, a large mumps outbreak occurred on the U.S. Territory of Guam during 2009-2010, primarily in school-aged children. METHODS: We implemented active surveillance in April 2010 during the outbreak peak and characterized the outbreak epidemiology. We administered third doses of MMR vaccine to eligible students aged 9-14 years in 7 schools with the highest attack rates (ARs) between 5/18/2010-5/21/2010. Baseline surveys, follow-up surveys, and case-reports were used to determine mumps vaccine ARs. Adverse events post-vaccination were monitored. RESULTS: Between 12/1/2009-12/31/2010, 505 mumps cases were reported. Self-reported Pohnpeians and Chuukese had the highest relative risks (54.7 and 19.7, respectively) and highest crowding indices (mean: 3.1 and 3.0 persons/bedroom, respectively). Among 287 (57%) school-aged case-patients, 270 (93%) had ≥2 MMR doses. A third MMR dose was administered to 1068 (33%) eligible students. Three-dose vaccinated students had an AR of 0.9/1000 compared with 2.4/1000 among students vaccinated with ≤2 doses more than1 incubation period pos-intervention, but the difference was not significant (p= 0.67). No serious adverse events were reported. CONCLUSIONS: This mumps outbreak occurred in a highly vaccinated population. The highest ARs occurred in ethnic minority populations with the highest household crowding indices. After the third dose MMR intervention in highly affected schools, three-dose recipients had an AR 60% lower than students with ≤2 doses, but the difference was not statistically significant and the intervention occurred after the outbreak peaked. This outbreak may have persisted due to crowding at home and high student contact rates. |
Economic impact of the 2009-2010 Guam mumps outbreak on the public health sector and affected families
Mahamud A , Fiebelkorn AP , Nelson G , Aguon A , McKenna J , Villarruel G , Gallagher K , Ortega-Sanchez IR . Vaccine 2012 30 (45) 6444-8 BACKGROUND: The United States Territory of Guam reported a large mumps outbreak of 505 cases during 2009-2010. We assessed the economic impact of the outbreak from the perspectives of the local public health sector and affected families. METHODS: Using standard cost analysis methods, we retrospectively identified all public health personnel involved in the outbreak response and surveyed them about their outbreak-related activities. We then estimated the costs of outbreak-related personnel hours and materials. We also assessed out-of-pocket costs and costs incurred for work-time missed for persons with mumps and their families. We defined the analysis period as February 25-October 22, 2010. RESULTS: Seventy-six public health personnel were involved in outbreak response activities. Overall, the response required approximately 8264 person-hours, 2380 miles driven, and 3000 doses of measles-mumps-rubella vaccine ordered. The cost to the public health sector was 256,785 U.S. dollars (USD). Families of 102 persons with mumps were interviewed. An estimated 761 USD per person with mumps was spent by families; 88% of this cost was due to missed days of work. The estimated total cost to families of the 470 persons with mumps during the analysis period was 357,670 USD. Total outbreak-related costs were 614,455 USD. CONCLUSIONS: The costs reported underscore the impact of mumps outbreaks in highly vaccinated populations and the need for effective mumps prevention and control strategies. |
Challenges in confirming a varicella outbreak in the two-dose vaccine era
Mahamud A , Wiseman R , Grytdal S , Basham C , Asghar J , Dang T , Leung J , Lopez A , Schmid DS , Bialek SR . Vaccine 2012 30 (48) 6935-9 BACKGROUND: A second dose of varicella vaccine was recommended for the U.S. children in 2006. We investigated a suspected varicella outbreak in School District X, Texas to determine 2-dose varicella vaccine effectiveness (VE). METHODS: A varicella case was defined as an illness with maculopapulovesicular rash without other explanation with onset during April 1-June 10, 2011, in a School District X student. We conducted a retrospective cohort in the two schools with the majority of cases. Lesion, saliva, and environmental specimens were collected for varicella-zoster virus (VZV) PCR testing. VE was calculated using historic attack rates among unvaccinated. RESULTS: In School District X, 82 varicella cases were reported, including 60 from Schools A and B. All cases were mild, with a median of 14 lesions. All 10 clinical specimens and 58 environmental samples tested negative for VZV. Two-dose varicella vaccination coverage was 66.4% in Schools A and B. Varicella VE in affected classrooms was 80.9% (95% CI: 67.2-88.9) among 1-dose vaccinees and 94.7% (95% CI: 89.2-97.4) among 2-dose vaccinees in School A, with a second dose incremental VE of 72.1% (95% CI: 39.0-87.3). Varicella VE among School B students did not differ significantly by dose (80.1% vs. 84.2% among 1-dose and 2-dose vaccines, respectively). CONCLUSION: Laboratory testing could not confirm varicella as the etiology of this outbreak; clinical and epidemiologic data suggests varicella as the likely cause. Better diagnostics are needed for diagnosis of varicella in vaccinated individuals so that appropriate outbreak control measures can be implemented. |
Herpes zoster-related deaths in the United States: validity of death certificates and mortality rates 1979-2007
Mahamud A , Marin M , Nickell SP , Shoemaker T , Zhang JX , Bialek SR . Clin Infect Dis 2012 55 (7) 960-6 BACKGROUND: Herpes zoster (HZ) vaccine was recommended in the United States to reduce HZ-associated morbidity. Vaccination may reduce HZ-associated mortality, but no strategy exists to monitor mortality trends. METHODS: We validated HZ coding on death certificates from California, using hospital records as the gold standard, and applied the results to national-level data to estimate HZ mortality. RESULTS: In the validation phase of the study, among 40 available hospital records listing HZ as the underlying cause of death, HZ was the underlying cause for 21 (52.5%) and a contributing cause for 5 (12.5%). Among 21 hospital records listing HZ as the underlying cause of death, the median age of decedents was 84 years (range 50-99); 60% had no contraindications for HZ vaccination. Of the 37 available records listing HZ as a contributing cause of death, HZ was a contributing cause for 2 (5.4%) and the underlying cause for 6 (16.2%). Nationally, in the 7 years preceding the HZ vaccination program, the average annual number of deaths in which HZ was reported as the underlying cause of death was 149; however, based on our validation study, we estimate the true number was 78 (range: 31-118). CONCLUSION: National death certificate data greatly overestimate deaths in which HZ is the underlying or contributing cause of death. The HZ vaccination program could prevent some HZ-related deaths but the impact will be difficult to assess using national mortality data. |
Epidemic cholera in Kakuma Refugee Camp, Kenya, 2009: the importance of sanitation and soap
Mahamud AS , Ahmed JA , Nyoka R , Auko E , Kahi V , Ndirangu J , Nguhi M , Burton JW , Muhindo BZ , Breiman RF , Eidex RB . J Infect Dev Ctries 2012 6 (3) 234-41 INTRODUCTION: Cholera remains a major public health problem that causes substantial morbidity and mortality in displaced populations due to inadequate or unprotected water supplies, poor sanitation and hygiene, overcrowding, and limited resources. A cholera outbreak with 224 cases and four deaths occurred in Kakuma Refugee Camp in Kenya from September to December 2009. METHODOLOGY: We conducted a case-control study to characterize the epidemiology of the outbreak. Cases were identified by reviewing the hospital registry for patients meeting the World Health Organization (WHO) case definition for cholera. For each case a matched control was selected. A questionnaire focusing on potential risk factors was administered to cases and controls. RESULTS: From 18 September to 15 December 2009, a total of 224 cases were identified and were hospitalised at Kakuma IRC hospital. Three refugees and one Kenyan national died of cholera. V. cholerae O1, serotype Inaba was isolated in 44 (42%) out of 104 stool specimens collected. A total of 93 cases and 93 matched controls were enrolled in the study. In a multivariate model, washing hands with soap was protective against cholera (adjusted odds ratio [AOR] =0.25[0.09-0.71]; p < 0.01), while presence of dirty water storage containers was a risk factor (AOR=4.39[1.12-17.14]; p=0.03). CONCLUSION: Provision of soap, along with education on hand hygiene and cleaning water storage containers, may be an affordable intervention to prevent cholera. |
Epidemiology of respiratory viral infections in two long-term refugee camps in Kenya, 2007-2010
Ahmed JA , Katz MA , Auko E , Njenga MK , Weinberg M , Kapella BK , Burke H , Nyoka R , Gichangi A , Waiboci LW , Mahamud A , Qassim M , Swai B , Wagacha B , Mutonga D , Nguhi M , Breiman RF , Eidex RB . BMC Infect Dis 2012 12 (1) 7 BACKGROUND: Refugees are at risk for poor outcomes from acute respiratory infections (ARI) because of overcrowding, suboptimal living conditions, and malnutrition. We implemented surveillance for respiratory viruses in Dadaab and Kakuma refugee camps in Kenya to characterize their role in the epidemiology of ARI among refugees. METHODS: From 1 September 2007 through 31 August 2010, we obtained nasopharyngeal (NP) and oropharyngeal (OP) specimens from patients with influenza-like illness (ILI) or severe acute respiratory infections (SARI) and tested them by RT-PCR for adenovirus (AdV), respiratory syncytial virus (RSV), human metapneumovirus (hMPV), parainfluenza viruses (PIV), and influenza A and B viruses. Definitions for ILI and SARI were adapted from those of the World Health Organization. Proportions of cases associated with viral etiology were calculated by camp and by clinical case definition. In addition, for children <5 years only, crude estimates of rates due to SARI per 1000 were obtained. RESULTS: We tested specimens from 1815 ILI and 4449 SARI patients (median age=1 year). Proportion positive for virus were AdV, 21.7%; RSV, 12.5%; hMPV, 5.7%; PIV, 9.4%; influenza A, 9.7%; and influenza B, 2.6%; 49.8% were positive for at least one virus. The annual rate of SARI hospitalization for 2007-2010 was 57 per 1000 children per year. Virus-positive hospitalization rates were 14 for AdV; 9 for RSV; 6 for PIV; 4 for hMPV; 5 for influenza A; and 1 for influenza B. The rate of SARI hospitalization was highest in children <1 year old (156 per 1000 child-years). The ratio of rates for children <1 year and 1 to <5 years old was 3.7:1 for AdV, 5.5:1 for RSV, 4.4:1 for PIV, 5.1:1 for hMPV, 3.2:1 for influenza A, and 2.2:1 for influenza B. While SARI hospitalization rates peaked from November to February in Dadaab, no distinct seasonality was observed in Kakuma. CONCLUSIONS: Respiratory viral infections, particularly RSV and AdV, were associated with high rates of illness and make up a substantial portion of respiratory infection in these two refugee settings. |
Comparison of nasopharyngeal and oropharyngeal swabs for the diagnosis of eight respiratory viruses by real-time reverse transcription-PCR assays
Kim C , Ahmed JA , Eidex RB , Nyoka R , Waiboci LW , Erdman D , Tepo A , Mahamud AS , Kabura W , Nguhi M , Muthoka P , Burton W , Breiman RF , Njenga MK , Katz MA . PLoS One 2011 6 (6) e21610 BACKGROUND: Many acute respiratory illness surveillance systems collect and test nasopharyngeal (NP) and/or oropharyngeal (OP) swab specimens, yet there are few studies assessing the relative measures of performance for NP versus OP specimens. METHODS: We collected paired NP and OP swabs separately from pediatric and adult patients with influenza-like illness or severe acute respiratory illness at two respiratory surveillance sites in Kenya. The specimens were tested for eight respiratory viruses by real-time reverse transcription-polymerase chain reaction (qRT-PCR). Positivity for a specific virus was defined as detection of viral nucleic acid in either swab. RESULTS: Of 2,331 paired NP/OP specimens, 1,402 (60.1%) were positive for at least one virus, and 393 (16.9%) were positive for more than one virus. Overall, OP swabs were significantly more sensitive than NP swabs for adenovirus (72.4% vs. 57.6%, p<0.01) and 2009 pandemic influenza A (H1N1) virus (91.2% vs. 70.4%, p<0.01). NP specimens were more sensitive for influenza B virus (83.3% vs. 61.5%, p = 0.02), parainfluenza virus 2 (85.7%, vs. 39.3%, p<0.01), and parainfluenza virus 3 (83.9% vs. 67.4%, p<0.01). The two methods did not differ significantly for human metapneumovirus, influenza A (H3N2) virus, parainfluenza virus 1, or respiratory syncytial virus. CONCLUSIONS: The sensitivities were variable among the eight viruses tested; neither specimen was consistently more effective than the other. For respiratory disease surveillance programs using qRT-PCR that aim to maximize sensitivity for a large number of viruses, collecting combined NP and OP specimens would be the most effective approach. |
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