This report updates the 2009 recommendations by CDC's Advisory Committee on Immunization Practices (ACIP) regarding the use of influenza vaccine for the prevention and control of influenza (CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2009;58[No. RR-8] and CDC. Use of influenza A (H1N1) 2009 monovalent vaccine---recommendations of the Advisory Committee on Immunization Practices [ACIP], 2009. MMWR 2009;58:[No. RR-10]). The 2010 influenza recommendations include new and updated information. Highlights of the 2010 recommendations include 1) a recommendation that annual vaccination be administered to all persons aged >or=6 months for the 2010-11 influenza season; 2) a recommendation that children aged 6 months--8 years whose vaccination status is unknown or who have never received seasonal influenza vaccine before (or who received seasonal vaccine for the first time in 2009-10 but received only 1 dose in their first year of vaccination) as well as children who did not receive at least 1 dose of an influenza A (H1N1) 2009 monovalent vaccine regardless of previous influenza vaccine history should receive 2 doses of a 2010-11 seasonal influenza vaccine (minimum interval: 4 weeks) during the 2010--11 season; 3) a recommendation that vaccines containing the 2010-11 trivalent vaccine virus strains A/California/7/2009 (H1N1)-like (the same strain as was used for 2009 H1N1 monovalent vaccines), A/Perth/16/2009 (H3N2)-like, and B/Brisbane/60/2008-like antigens be used; 4) information about Fluzone High-Dose, a newly approved vaccine for persons aged >or=65 years; and 5) information about other standard-dose newly approved influenza vaccines and previously approved vaccines with expanded age indications. Vaccination efforts should begin as soon as the 2010-11 seasonal influenza vaccine is available and continue through the influenza season. These recommendations also include a summary of safety data for U.S.-licensed influenza vaccines. These recommendations and other information are available at CDC's influenza website (http://www.cdc.gov/flu); any updates or supplements that might be required during the 2010-11 influenza season also will be available at this website. Recommendations for influenza diagnosis and antiviral use will be published before the start of the 2010-11 influenza season. Vaccination and health-care providers should be alert to announcements of recommendation updates and should check the CDC influenza website periodically for additional information.

BACKGROUND: The Ryan White HIV/AIDS Program (RWHAP) provides HIV-infected persons with services not covered by other healthcare payer types. Limited data exist to inform policy decisions about the most appropriate role for RWHAP under the Patient Protection and Affordable Care Act (ACA). METHODS: We assessed associations between RWHAP assistance and antiretroviral therapy (ART) prescription and viral suppression. We used data from the Medical Monitoring Project (MMP), a surveillance system assessing characteristics of HIV-infected adults receiving medical care in the United States. Interview and medical record data were collected in 2009-2013from 18,095patients. RESULTS: Nearly 41% of patients had RWHAP assistance; 15% relied solely on RWHAP assistance for HIV care. Overall, 91% were prescribed ART, and 75% were virally suppressed. Uninsured patients receiving RWHAP assistance were significantly more likely to be prescribed ART (52% versus 94%; P<0.01) and virally suppressed (39% versus 77%; P<0.01) than uninsured patients without RWHAP assistance. Patients with private insurance and Medicaid were 6% and 7% less likely, respectively, to be prescribed ART than those with RWHAP only (P<0.01). Those with private insurance and Medicaid were 5% and 12% less likely, respectively, to be virally suppressed (P≤0.02) than those with RWHAP only. Patients whose private or Medicaid coverage was supplemented by RWHAP were more likely to be prescribed ART and virally suppressed than those without RWHAP supplementation (P≤0.01). CONCLUSIONS: Uninsured and underinsured HIV-infected persons receiving RWHAP assistance were more likely to be prescribed ART and virally suppressed than those with other types of healthcare coverage.

CONTEXT: Immunizations are the most effective way to reduce incidence of vaccine-preventable diseases. Immunization information systems (IISs) are confidential, population-based, computerized databases that record all vaccination doses administered by participating providers to people residing within a given geopolitical area. They facilitate consolidation of vaccination histories for use by health care providers in determining appropriate client vaccinations. Immunization information systems also provide aggregate data on immunizations for use in monitoring coverage and program operations and to guide public health action. EVIDENCE ACQUISITION: Methods for conducting systematic reviews for the Guide to Community Preventive Services were used to assess the effectiveness of IISs. Reviewed evidence examined changes in vaccination rates in client populations or described expanded IIS capabilities related to improving vaccinations. The literature search identified 108 published articles and 132 conference abstracts describing or evaluating the use of IISs in different assessment categories. EVIDENCE SYNTHESIS: Studies described or evaluated IIS capabilities to (1) create or support effective interventions to increase vaccination rates, such as client reminder and recall, provider assessment and feedback, and provider reminders; (2) determine client vaccination status to inform decisions by clinicians, health care systems, and schools; (3) guide public health responses to outbreaks of vaccine-preventable disease; (4) inform assessments of vaccination coverage, missed vaccination opportunities, invalid dose administration, and disparities; and (5) facilitate vaccine management and accountability. CONCLUSIONS: Findings from 240 articles and abstracts demonstrate IIS capabilities and actions in increasing vaccination rates with the goal of reducing vaccine-preventable disease.

INTRODUCTION: During the 2009-2010 H1N1 pandemic, vaccine in short supply was allocated to states pro rata by population, yet the vaccination rates of adults differed by state. States also differed in their campaign processes and decisions. Analyzing the campaign provides an opportunity to identify specific approaches that may result in higher vaccine uptake in a future event of this nature. OBJECTIVE: To determine supply chain and system factors associated with higher state H1N1 vaccination coverage for adults in a system where vaccine was in short supply. METHODS: Regression analysis of factors predicting state-specific H1N1 vaccination coverage in adults. Independent variables included state campaign information, demographics, preventive or health-seeking behavior, preparedness funding, providers, state characteristics, and H1N1-specific state data. RESULTS: The best model explained the variation in state-specific adult vaccination coverage with an adjusted R-squared of 0.76. We found that higher H1N1 coverage of adults is associated with program aspects including shorter lead-times (i.e., the number of days between when doses were allocated to a state and were shipped, including the time for states to order the doses) and less vaccine directed to specialist locations. Higher vaccination coverage is also positively associated with the maximum number of ship-to locations, past seasonal influenza vaccination coverage, the percentage of women with a Pap smear, the percentage of the population that is Hispanic, and negatively associated with a long duration of the epidemic peak. CONCLUSION: Long lead-times may be a function of system structure or of efficiency and may suggest monitoring or redesign of distribution processes. Sending vaccine to sites with broad access could be useful when covering a general population. Existing infrastructure may be reflected in the maximum number of ship-to locations, so strengthening routine influenza vaccination programs may help during emergency vaccinations also. Future research could continue to inform program decisions.

INTRODUCTION: During the 2009-2010 H1N1 pandemic, children and high-risk adults had priority for vaccination. Vaccine in short supply was allocated to states pro-rata by population, but vaccination rates as of January 2010 varied among states from 21.3% to 84.7% for children and 10.4% to 47.2% for high-risk adults. States had different campaign processes and decisions. OBJECTIVE: To determine program and system factors associated with higher state pandemic vaccination coverage for children and high-risk adults during an emergency response with short supply of vaccine. METHODS: Regression analysis of factors predicting state-specific H1N1 vaccination coverage in children and high-risk adults, including state campaign information, demographics, preventive or health-seeking behavior, preparedness funding, providers, state characteristics, and surveillance data. RESULTS: Our modeling explained variation in state-specific vaccination coverage with an adjusted R-squared of 0.82 for children and 0.78 for high-risk adults. We found that coverage of children was positively associated with programs focusing on school clinics and with a larger proportion of doses administered in public sites; negatively with the proportion of children in the population, and the proportion not visiting a doctor because of cost. The coverage for high-risk adults was positively associated with shipments of vaccine to "general access" locations, including pharmacy and retail, with the percentage of women with a Pap smear within the past 3 years and with past seasonal influenza vaccination. It was negatively associated with the expansion of vaccination to the general public by December 4, 2009. For children and high-risk adults, coverage was positively associated with the maximum number of ship-to-sites and negatively associated with the proportion of medically underserved population. CONCLUSION: Findings suggest that distribution and system decisions such as vaccination venues and providers targeted can positively impact vaccination rates for children and high-risk adults. Additionally, existing health infrastructure, health-seeking behaviors, and access affected coverage.

BACKGROUND: Racial/ethnic disparities in influenza vaccination among adults are longstanding, and research suggests they result from multiple factors. Influenza vaccine-seeking behavior may be an important aspect to consider when evaluating disparities in vaccination coverage. OBJECTIVE: To determine whether there are differences between blacks and whites in influenza vaccine-seeking behavior among adults 65 years and older. METHODS: Data were analyzed from a national sample of 3138 adults 65 years and older collected through the adult module of the 2007 National Immunization Survey, a random digit dialing telephone survey, which included an oversample of non-Hispanic blacks. Analysis included influenza vaccination rate, location of vaccination, and whether vaccinated individuals specifically went to the location to receive the vaccine (vaccine seekers) by race. The relationship between attitudes about influenza vaccination and vaccine-seeking behavior by race was also examined. RESULTS: White adults 65 years and older were significantly more likely to receive influenza vaccine than blacks, during the 2006-2007 influenza season (68% +/- 4% vs 54% +/- 3%, respectively), and a significantly higher proportion of vaccinated whites reported seeking out the vaccine than vaccinated blacks (66% +/- 4% vs 47% +/- 4%, respectively). Blacks were less likely to be vaccine seekers, regardless of education or poverty levels. Among persons vaccinated in a doctor's office, 52% of whites specifically went there to get vaccinated, compared with 37% of blacks. Among persons who believe the vaccine is very effective, 66% +/- 5% of whites versus 50% +/- 6% of blacks were vaccine seekers. CONCLUSIONS: This study points to the importance of improving our understanding of what factors, in addition to beliefs about vaccination, lead to vaccine seeking and reinforces the need for systematically offering vaccine.

BACKGROUND: Knowledge and beliefs about influenza vaccine that differ across racial or ethnic groups may promote racial or ethnic disparities in vaccination. OBJECTIVE: To identify associations between vaccination behavior and personal beliefs about influenza vaccine by race or ethnicity and education levels among the U.S. elderly population. METHODS: Data from a national telephone survey conducted in 2004 were used for this study. Reponses for 3875 adults ≥65 years of age were analyzed using logistic regression methods. RESULTS: Racial and ethnic differences in beliefs were observed. For example, whites were more likely to believe influenza vaccine is very effective in preventing influenza compared to blacks and Hispanics (whites, 60%; blacks, 47%, and Hispanics, 51%, p<0.01). Among adults who believed the vaccine is very effective, self-reported vaccination was substantially higher across all racial/ethnic groups (whites, 93%; blacks, 76%; Hispanics, 78%) compared to adults who believed the vaccine was only somewhat effective (whites 67%; blacks 61%, Hispanics 61%). Also, vaccination coverage differed by education level and personal beliefs of whites, blacks, and Hispanics. CONCLUSIONS: Knowledge and beliefs about influenza vaccine may be important determinants of influenza vaccination among racial/ethnic groups. Strategies to increase coverage should highlight the burden of influenza disease in racial and ethnic populations, the benefits and safety of vaccinations and personal vulnerability to influenza disease if not vaccinated. For greater effectiveness, factors associated with the education levels of some communities may need to be considered when developing or implementing new strategies that target specific racial or ethnic groups.

OBJECTIVE: To assess the level of participation of endocrinologists in the United States in the 2009 to 2010 H1N1 vaccination campaign and explore their perspectives on H1N1 vaccination. METHODS: We conducted a cross-sectional, mailed survey of a national sample of 1,991 endocrinologists in June through September 2010. The extent of the response and the survey responses are reported and analyzed. RESULTS: The overall response rate was 59%. The majority of endocrinologists strongly recommended H1N1 vaccine for children, whereas about a third did so for both nonelderly adults and seniors. Just over half (52%) of the responding endocrinologists had agreed to participate in the 2009 to 2010 H1N1 vaccine campaign and received vaccine, in comparison with 73% who offered seasonal influenza vaccine. The supply of H1N1 vaccine was a significant challenge, but otherwise endocrinologists reported few major problems with administration of H1N1 vaccine. Overall, less than half of the respondents thought that they would be "very likely" to provide vaccine in the event of a future influenza pandemic, with a much higher proportion among those endocrinologists who offered seasonal influenza vaccine and H1N1 vaccine. CONCLUSION: Although the experiences of endocrinologists who provided H1N1 vaccine were generally positive, many did not offer the vaccine and indicated that they are hesitant about providing vaccine during a future influenza pandemic. Approaches to increase their participation in future pandemics in an effort to reach persons at high risk for influenza and its complications, such as those with diabetes, should be further explored.

Persons with high-risk conditions such as asthma were a target group for H1N1 vaccine recommendations. We conducted a mailed survey of a national sample of pulmonologists to understand their participation in the 2009-2010 H1N1 vaccine campaign. The response rate was 59%. The majority of pulmonologists strongly recommended H1N1 vaccine for children (73%) and adults aged 25-64 years (51%). Only 60% of respondents administered H1N1 vaccine in their practice compared to 87% who offered seasonal influenza vaccine. Other than vaccine supply, respondents who provided H1N1 vaccine reported few logistical problems. Two-thirds of respondents would be very likely to vaccinate during a future influenza pandemic; this rate was higher among those who provided H1N1 vaccine and/or seasonal flu vaccine. In total, the H1N1 vaccine-related experiences of pulmonologists seemed to be positive. However, additional efforts are needed to increase participation in future pandemic vaccination campaigns.

As the preceding articles indicate, school-located vaccination (SLV) shows great promise as a method to quickly and efficiently vaccinate large numbers of school-aged children against influenza. This approach can both relieve health care providers who lack sufficient capacity to effectively vaccinate their patients annually, in accordance with the 2008 recommendations of Advisory Committee on Immunization Practices (ACIP),1 as well as provide a convenient option for parents and an opportunity for children without a medical home to be vaccinated. Importantly, SLV may be appropriate for routine vaccination against seasonal influenza, as well as during a public health emergency or pandemic. | The utility of SLV was demonstrated on a large scale in response to the 2009–2010 H1N1 influenza pandemic. In July 2009, intense efforts were underway to procure H1N1 vaccine and prepare for implementing a large-scale national vaccination program. At that time, the ACIP published recommendations that defined the highest-priority target groups to receive vaccine when it first became available, which included school-aged children.2 Accordingly, public health units, educational institutions, and others in local communities joined together to hold SLV clinics throughout the United States, with several states implementing SLV statewide. Based on a National Association of County and City Health Officials survey of local health department officials that was conducted in the summer of 2010, an estimated 85% of local health departments held at least 1 H1N1 influenza SLV clinic in their jurisdiction (National Association of County and City Health Officials, unpublished data). The Centers for Disease Control and Prevention’s (CDC) National 2009 H1N1 Flu Survey is a nationally representative telephone-based survey designed to collect vaccination coverage from US households.3 This survey indicated that 37% of school-aged children 5- to17-years-old received 2009 H1N1 influenza vaccination; approximately one-third of these children were vaccinated at school (CDC, unpublished data).

BACKGROUND: Persons with high-risk conditions such as asthma were a target group for national H1N1 vaccine recommendations. Allergists/immunologists (allergists) are a provider group that could vaccinate persons with asthma and other high-risk conditions. Their level of participation in and experiences with the 2009-2010 H1N1 vaccination campaign are unknown. OBJECTIVE: To describe the experiences of allergists related to the 2009-2010 H1N1 vaccination campaign. METHODS: A cross-sectional, mailed survey of a national sample of 1955 allergists providing outpatient care was conducted in June-September 2010. RESULTS: The overall response rate was 72%. Most allergists "strongly recommended" H1N1 vaccine for children, and most "recommended" or "strongly recommended" vaccine for adults. The majority (71%) agreed to participate in the H1N1 vaccine campaign and received vaccine. Vaccine supply was a significant challenge, but otherwise few major problems were experienced with administering H1N1 vaccine. The majority of respondents, particularly among those who participated in the 2009-2010 H1N1 vaccination campaign, felt they would be very likely to vaccinate in the event of future influenza pandemic. CONCLUSION: The experiences of allergists in the H1N1 vaccine campaign were generally positive. Most allergists are willing to serve as vaccinators in future influenza pandemics, which will help facilitate broad access to vaccine for patients with asthma and other high-risk conditions.

During the 2009 H1N1 influenza pandemic, the CDC contacted the 50 state, New York City, and District of Columbia health departments and the health department in Puerto Rico through the Association of State and Territorial Health Officials (ASTHO), to discuss distributing 2009 H1N1 influenza vaccine directly to large pharmacy chains (“pharmacies”) to supplement state vaccination efforts. By the end of December 2009, most states had opened vaccination to all members of the public and a vaccine surplus was projected. All but three states opted to take part in this CDC 2009 H1N1 Vaccine Pharmacy Initiative.* The CDC subsequently invited the largest 15 US pharmacies (by prescription share) to participate, 12 of these pharmacies expressed interest and 10 ultimately participated.1 From December 2009-February 2010, the CDC distributed 5 483 900 doses of 2009 H1N1 vaccine to these pharmacy chains; they in turn, distributed it to more than 10 700 retail stores nationwide. The amount of 2009 H1N1 vaccine that the CDC directly distributed to pharmacy chains comprised approximately 23% of all vaccine distributed during the same time period to the same states and accounted for approximately 4.3% of all 2009 H1N1 vaccine distributed during October 2009-February 2010. Approximately 10% of adults who received 2009 H1N1 influenza vaccine reported getting vaccinated at a pharmacy.2 This included vaccinations given with vaccine provided to pharmacies by state health officials and directly by the CDC (Figure).

BACKGROUND: From 2005 through 2007, 3 vaccines were added to the adolescent vaccination schedule: tetanus-diphtheria-acellular pertussis (TdaP); meningococcal conjugate (MenACWY); and human papillomavirus (HPV) for girls. OBJECTIVE: To assess implementation of new adolescent vaccination recommendations. METHODS: Data from the 2006-2009 National Immunization Survey-Teen, an annual provider-verified random-digit-dial survey of vaccination coverage in US adolescents aged 13 to 17 years, were analyzed. Main outcome measures included percentage of adolescents who received each vaccine according to survey year; potential coverage if all vaccines were administered during the same vaccination visit; and, among unvaccinated adolescents, the reasons for not receiving vaccine. RESULTS: Between 2006 and 2009, ≥1 TdaP and ≥1 MenACWY coverage increased from 11% to 56% and 12% to 54%, respectively. Between 2007 and 2009, ≥1 HPV coverage among girls increased from 25% to 44%; between 2008 and 2009, ≥3 HPV coverage increased from 18% to 27%. In 2009, vaccination coverage could have been >80% for Td/TdaP and MenACWY and as high as 74% for the first HPV dose if providers had administered all recommended vaccines during the same vaccination visit. For all years, the top reported reasons for not vaccinating were no knowledge about the vaccine, provider did not recommend, and vaccine is not needed/necessary (for TdaP and MenACWY) and adolescent is not sexually active, no knowledge about the vaccine, and vaccine is not needed/necessary (for HPV). CONCLUSIONS: Adolescent vaccination coverage is increasing but could be improved. Strategies are needed to increase parental knowledge about adolescent vaccines and improve provider recommendation and administration of all vaccines during the same visit.

In 2011, institutional requirements for pertussis vaccination of healthcare personnel were reported by nearly one-third of surveyed US hospitals. Requirements often applied to personnel with certain clinical responsibilities, such as those caring for infants. Healthcare personnel who were not on an institution's payroll were rarely subject to pertussis vaccination requirements.

BACKGROUND: Many health professional organizations now endorse influenza vaccination as a condition of employment in healthcare settings. Our objective was to describe institutional requirements for influenza vaccination of healthcare personnel (HCP) among US hospitals during the 2010-2011 influenza season. METHODS: A survey was mailed in 2011 to a nationally representative sample of 998 acute care hospitals. An institutional requirement was defined as "a policy that requires HCP to receive or decline influenza vaccination, with or without consequences for vaccine refusal." A weighted analysis included univariate analyses and logistic regression. RESULTS: Of responding hospitals (n = 808; 81.0%), 440 (55.6%) reported institutional requirements for influenza vaccination. Although employees were uniformly subject to requirements, nonemployees often were not. The proportion of requirements with consequences for vaccine refusal was 44.4% (n = 194); where consequences were imposed, nonmedical exemptions were often granted (69.3%). Wearing a mask was the most common consequence (74.2% of 194 requirements); by contrast, 29 hospitals (14.4%) terminated unvaccinated HCP. After adjustment for demographic factors, the following characteristics remained significantly associated with requirements: location in a state requiring HCP to receive or decline influenza vaccine, caring for inpatients that are potentially vulnerable to influenza, use of ≥9 Advisory Committee on Immunization Practices-recommended, evidence-based influenza vaccination campaign strategies, and for-profit ownership. CONCLUSIONS: Influenza vaccination requirements were prevalent among hospitals of varying size and location. However, few policies were as stringent or as comprehensive as those endorsed by health professional organizations. Because influenza vaccination requirements are a viable alternative for hospitals unable to achieve high coverage through voluntary policies, there is still substantial room for improvement.

BACKGROUND: Institutional requirements for influenza vaccination, ranging from policies that mandate declinations to those terminating unvaccinated healthcare personnel (HCP), are increasingly common in the US. Our objective was to determine HCP vaccine uptake following requirements for influenza vaccination at US hospitals. METHODS: Survey mailed in 2011 to a nationally representative sample of 998 acute care hospitals. An institutional requirement was defined as an institutional policy that requires receipt or declination of influenza vaccination, with or without consequences for vaccine refusal. Respondents reported institutional-level, seasonal influenza vaccination coverage, if known, during two consecutive influenza seasons: the season prior to (i.e., pre-requirement), and the first season of requirement (i.e., post-requirement). Weighted univariate and multivariate analyses accounted for sampling design and non-response. RESULTS: 808 (81.0%) hospitals responded. Of hospitals with institutional requirements for influenza vaccination (n=440), 228 hospitals met analytic inclusion criteria. Overall, mean reported institutional-level influenza vaccination coverage among HCP rose from 62.0% in the pre-requirement season to 76.6% in the post-requirement season, representing a single-season increase of 14.7 (95% CI: 12.6-16.7) percentage points. After adjusting for potential confounders, single-season increases in influenza vaccination uptake remained greater among hospitals that imposed consequences for vaccine refusal, and among hospitals with lower pre-requirement vaccination coverage. Institutional characteristics were not associated with vaccination increases of differential magnitude. CONCLUSION: Hospitals that are unable to improve suboptimal influenza vaccination coverage through multi-faceted, voluntary vaccination campaigns may consider institutional requirements for influenza vaccination. Rapid and measurable increases in vaccination coverage followed institutional requirements at hospitals of varying demographic characteristics.

US health professional schools with student immunity requirements for recommended vaccines frequently accept evidence of immunity other than vaccination but vary widely on the types of evidence that are accepted. Exemptions for nonmedical reasons and, to a lesser extent, medical reasons are often obtainable by a student-written document.

BACKGROUND: In February 2005, the US Advisory Committee on Immunization Practices recommended the new meningococcal conjugate vaccine (MCV4) for routine use among 11- to 12-year-olds (at the preadolescent health-care visit), 14- to 15-year-olds (before high-school entry), and groups at increased risk. Vaccine distribution started in March; however, in July, the manufacturer reported inability to meet demand and widespread MCV4 shortages were reported. Our objectives were to determine early uptake patterns among target (11-12 and 14-15 year olds) and non-target (13- plus 16-year-olds) age groups. A post hoc analysis was conducted to compare seasonal uptake patterns of MCV4 with polysaccharide meningococcal (MPSV4) and tetanus diphtheria (Td) vaccines. METHODS: We analyzed data for adolescents 11-16 years from five managed care organizations participating in the Vaccine Safety Datalink (VSD). For MCV4, we estimated monthly and cumulative coverage during 2005 and calculated risk ratios. For MPSV4 and Td, we combined 2003 and 2004 data and compared their seasonal uptake patterns with MCV4. RESULTS: Coverage for MCV4 during 2005 among the 623,889 11-16 years olds was 10%. Coverage for 11-12 and 14-15 year olds was 12% and 11%, respectively, compared with 8% for 13- plus 16-year-olds (p < 0.001). Of the 64,272 MCV4 doses administered from March-December 2005, 73% were administered June-August. Fifty-nine percent of all MPSV4 doses and 38% of all Td doses were administered during June-August. CONCLUSION: A surge in vaccine uptake between June and August was observed among adolescents for MCV4, MPSV4 and Td vaccines. The increase in summer-time vaccinations and vaccination of non-targeted adolescents coupled with supply limitations likely contributed to the reported shortages of MCV4 in 2005.

BACKGROUND: The influenza vaccination rate among US health care personnel (HCP) remains low and may vary by occupational categories. The objective of this study was to explore knowledge, attitudes, and beliefs associated with influenza vaccination in a broad population of registered nurses. METHODS: The study used a cross-sectional mail survey, administered January-March 2006, of 2000 registered nurses in 4 US states. RESULTS: Of the 2000 surveys sent, 1310 (72%) were returned, and 1017 (67%) were eligible for analysis. The majority of respondents (59%) reported receiving influenza vaccine during the 2005-2006 influenza season. The most common reason for being vaccinated was protecting oneself from illness (95%), and the most common reason for not being vaccinated was concern about adverse reactions (39%). Respondents who reported their patient population as high risk related to influenza were more likely to be vaccinated and to agree with statements regarding influenza disease and influenza vaccination of HCP. CONCLUSION: Concerns about adverse reactions and vaccine effectiveness continue to be barriers to influenza vaccination among registered nurses. Those most knowledgeable about influenza vaccination of HCP have higher vaccination rates. Future efforts to improve vaccination rates should include data on vaccine effectiveness and adverse effects, as well as descriptions of high-risk populations.