BACKGROUND: Few studies have examined the effectiveness of full vs. partial vaccination with inactivated trivalent influenza vaccines (IIV3) as defined by the U.S. CDC Advisory Committee on Immunization Practices (ACIP). METHODS: Respiratory swabs were collected from outpatients aged 6 months to 8 years with acute cough for ≤7 days in clinics in 5 states during the 2011-2012 and 2012-2013 influenza seasons. Influenza was confirmed by real-time reverse transcription polymerase chain reaction assay. Receipt of current season IIV3 and up to 4 prior vaccinations was documented from medical records and immunization registries. Using a test-negative design, vaccine effectiveness (VE) was estimated adjusting for age, race/ethnicity, medical conditions, study site, and month of enrollment. RESULTS: We did not observe higher VE for children fully vs. partially vaccinated with IIV3, as defined by U.S. ACIP, though our sample of partially vaccinated children was relatively small. However, among children aged 2-8 years in both seasons and against A(H3N2) and B influenza illness separately, VE point estimates were consistently higher for children who had received 2 doses in the same prior season compared to those without (VE range of 58-80% vs. 33-44%, respectively). Across seasons, the odds of A(H3N2) illness despite IIV3 vaccination were 2.4-fold (95% CI = 1.4-4.3) higher among children who had not received 2 doses in the same prior season. We also noted residual protection among unvaccinated children who were vaccinated the previous season (VE range = 36-40% across outcomes). CONCLUSION: Vaccination with IIV3 may provide preventive benefit in subsequent seasons, including possible residual protection if vaccination is missed. Two vaccine doses in the same season may be more effective than alternative priming strategies.

We evaluated the cycle threshold (CT) values of 1160 influenza A positive and 806 influenza B positive specimens from two seasons of the US Flu VE Network to identify factors associated with CT values. Low CT values (high genomic load) were associated with shorter intervals between illness onset and specimen collection, young age (ages 3-8 years old), and self-rated illness severity for both influenza A and B. Low CT values were also associated with reported fever/feverishness and age ≥65 years for influenza A.

During the 2013-14 influenza season, we analyzed data from 6,004 outpatients aged ≥6 months with acute respiratory illness (ARI). Among the 2,786 ARI patients at higher risk for influenza complications, 835 (30%) presented to care ≤2 days from symptom onset; among those, 126 (15%) were prescribed an antiviral medication.

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months. Each season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine in preventing medically attended acute respiratory illness (ARI) associated with laboratory-confirmed influenza. This season, early estimates of influenza vaccine effectiveness are possible because of widespread, early circulation of influenza viruses. By January 3, 2015, 46 states were experiencing widespread flu activity, with predominance of influenza A (H3N2) viruses. This report presents an initial estimate of seasonal influenza vaccine effectiveness at preventing laboratory-confirmed influenza virus infection associated with medically attended ARI based on data from 2,321 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (Flu VE) during November 10, 2014-January 2, 2015. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age, sex, race/ethnicity, self-rated health, and days from illness onset to enrollment) against laboratory-confirmed influenza associated with medically attended ARI was 23% (95% confidence interval [CI] = 8%-36%). Most influenza infections were due to A (H3N2) viruses. This interim VE estimate is relatively low compared with previous seasons when circulating viruses and vaccine viruses were well-matched and likely reflects the fact that more than two-thirds of circulating A (H3N2) viruses are antigenically and genetically different (drifted) from the A (H3N2) vaccine component of 2014-15 Northern Hemisphere seasonal influenza vaccines. These early, low VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with the currently circulating A (H3N2) viruses as well as other viruses that might circulate later in the season, including influenza B viruses. Even when VE is reduced, vaccination still prevents some illness and serious influenza-related complications, including thousands of hospitalizations and deaths. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated, including persons who might already have been ill with influenza this season.

BACKGROUND: During the 2012-13 influenza season, there was co-circulation of A/H3N2 and two B lineage viruses in the United States. METHODS: Patients with acute cough illness ≤7 days duration were prospectively enrolled and swabbed at outpatient clinics in five states. Influenza vaccination dates were confirmed by medical records. Vaccine effectiveness (VE) was estimated as [100% x (1-adjusted odds ratio)] for vaccination in cases vs. test-negative controls. RESULTS: Influenza was detected in 2,307 (36%) of 6,452 patients; 1,292 (56%) had A/H3N2, 582 (25%) had B/Yamagata, and 303 (13%) had B/Victoria. VE was 49% (95% CI: 43, 55) overall; 39% (95% CI: 29, 47) against A/H3N2, 66% (95% CI: 58, 73) against B/Yamagata (vaccine lineage), and 51% (95% CI: 36, 63) against B/Victoria. VE against A/H3N2 was highest among persons aged 50-64 years (52%; 95% CI: 33, 65) and 6 months-8 years (51%; 95% CI: 32, 64) and lowest among those ≥65 years (11%; 95% CI: -41, 43). In younger age groups, there was evidence of residual protection from receipt of the 2011-12 vaccine one year earlier. CONCLUSIONS: The 2012-13 vaccines were moderately effective in most age groups. Cross-lineage protection and residual effects from prior vaccination were observed and warrant further investigation.

CONTEXT: Rabies virus causes a fatal encephalitis and is typically acquired through the bite of an infected mammal. Rabies is preventable through administration of rabies postexposure prophylaxis (PEP), but this must be balanced with the need to avoid unnecessary PEP use. Though not nationally notifiable, some state health departments (SHDs) have made animal bites and use of PEP reportable within their jurisdictions. OBJECTIVE: We evaluated whether animal bites and PEP were reportable to SHDs as of 2013 for every state in the United States. DESIGN: The list of reportable conditions for each SHD as of 2013 was reviewed on the Internet for every state in the United States to determine whether animal bites or PEP were reportable. We then contacted an SHD representative (typically the State Public Health Veterinarian) to confirm data generated through Internet searches. Health departments in states where PEP was reportable were asked to complete a follow-up survey. RESULTS: Animal bites and PEP both were reportable in 9 states (18%). Another 9 states (18%) mandated animal bite reporting but not PEP reporting, while 12 states (24%) mandated PEP reporting but not animal bite reporting. These events were not reportable in 20 states (40%). The benefits reported by personnel from SHDs with PEP reporting systems varied greatly. CONCLUSIONS: Additional investigations focusing on the value of information returned by PEP reporting and identifying best practices for implementation and management are needed. The lack of standardization between current animal bite and PEP reporting systems limits completeness of reporting and comparability of outcomes. National recommendations to standardize case definitions and other data elements might help jurisdictions developing new animal bite or PEP reporting systems.

BACKGROUND: Early antiviral treatment (≤2 days since illness onset) of influenza reduces the probability of influenza-associated complications. Early empiric antiviral treatment is recommended for those with suspected influenza at higher risk for influenza complications regardless of their illness severity. We describe antiviral receipt among outpatients with acute respiratory illness (ARI) and antibiotic receipt among patients with influenza. METHODS: We analyzed data from 5 sites in the US Influenza Vaccine Effectiveness Network Study during the 2012-2013 influenza season. Subjects were outpatients aged ≥6 months with ARI defined by cough of ≤7 days' duration; all were tested for influenza by polymerase chain reaction (PCR). Medical history and prescription information were collected by medical and pharmacy records. Four sites collected prescribing data on 3 common antibiotics (amoxicillin-clavulanate, amoxicillin, and azithromycin). RESULTS: Of 6766 enrolled ARI patients, 509 (7.5%) received an antiviral prescription. Overall, 2366 (35%) had PCR-confirmed influenza; 355 (15%) of those received an antiviral prescription. Among 1021 ARI patients at high risk for influenza complications (eg, aged <2 years or ≥65 years or with ≥1 chronic medical condition) presenting to care ≤2 days from symptom onset, 195 (19%) were prescribed an antiviral medication. Among participants with PCR-confirmed influenza and antibiotic data, 540 of 1825 (30%) were prescribed 1 of 3 antibiotics; 297 of 1825 (16%) were prescribed antiviral medications. CONCLUSIONS: Antiviral treatment was prescribed infrequently among outpatients with influenza for whom therapy would be most beneficial; in contrast, antibiotic prescribing was more frequent. Continued efforts to educate clinicians on appropriate antibiotic and antiviral use are essential to improve healthcare quality.

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months. Each season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine to prevent influenza-associated, medically attended acute respiratory illness (ARI). This report uses data from 2,319 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness (Flu VE) Network during December 2, 2013-January 23, 2014, to estimate an interim adjusted effectiveness of seasonal influenza vaccine for preventing laboratory-confirmed influenza virus infection associated with medically attended ARI. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age, sex, race/ethnicity, self-rated health, and days from illness onset to enrollment) against influenza A and B virus infection associated with medically attended ARI was 61%. The influenza A (H1N1)pdm09 (pH1N1) virus that emerged to cause a pandemic in 2009 accounted for 98% of influenza viruses detected. VE was estimated to be 62% against pH1N1 virus infections and was similar across age groups. As of February 8, 2014, influenza activity remained elevated in the United States, the proportion of persons seeing their health-care provider for influenza-like illness was lower than in early January but remained above the national baseline, and activity still might be increasing in some parts of the country. CDC and the Advisory Committee on Immunization Practices routinely recommend that annual influenza vaccination efforts continue as long as influenza viruses are circulating. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated. Antiviral medications are an important second line of defense to treat influenza illness and should be used as recommended among suspected or confirmed influenza patients, regardless of patient vaccination status. Early antiviral treatment is recommended for persons with suspected influenza with severe or progressive illness (e.g., hospitalized persons) and those at high risk for complications from influenza, no matter how severe the illness.