Interim Results: Influenza A (H1N1) 2009 Monovalent and Seasonal Influenza Vaccination Coverage Among Health-Care Personnel --- United States, August 2009--January 2010

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Since 1986, the Healthcare Infection Control Practices Advisory Committee (HICPAC) and the Advisory Committee on Immunization Practices (ACIP) have recommended that all health-care personnel (HCP) be vaccinated annually for influenza (1,2). Since 1989, overall influenza vaccination coverage among HCP has never exceeded 49% in any season, according to estimates from the National Health Interview Survey (3,4). In August 2009, ACIP recommended that HCP be one of five initial target groups to receive the influenza A (H1N1) 2009 monovalent vaccine when it first became available (5). This report summarizes results of a population-based panel survey administered via the Internet during January 2010 to a nationally representative sample of 1,417 HCP to assess vaccination coverage. By mid-January 2010, estimated vaccination coverage among HCP was 37.1% for 2009 pandemic influenza A (H1N1) and 61.9% for seasonal influenza. Overall, 64.3% received either of these influenza vaccines, higher coverage than any previous season, but only 34.7% of HCP reported receiving both vaccines. The existence of an employer requirement for vaccination at the facility where the respondent was employed was associated with an eightfold greater likelihood of 2009 H1N1 vaccination compared with respondents employed by facilities with neither requirement nor recommendations; likewise, the existence of a recommendation for vaccination was associated with a fourfold greater probability of 2009 H1N1 vaccination. Health-care administrators should consider influenza vaccination coverage among employees an important measure of patient safety and make appropriate efforts to increase coverage in future seasons.

To monitor monthly influenza vaccination coverage among HCP through the 2009--10 influenza season, CDC has been collaborating with the RAND Corporation to collect monthly survey data on a nationally representative panel of HCP from December 1, 2009, to June 30, 2010. The panel, maintained by Knowledge Networks, Inc., consists solely of persons recruited using random-digit--dialing sampling methodology. Knowledge Networks uses the same quality standards for recruitment as the National Immunization Survey. Surveys are conducted online; access to the Internet and equipment are provided if needed; and participants are rewarded with nominal cash incentives.*

For the survey described in this report, the sample consisted of self-identified HCP drawn from the existing panel. Panelists were identified as either working in a health-care setting† or in a health-related profession based on responses to a screening questionnaire that was administered at the time of recruitment to the panel and periodically updated. Panelists were asked to describe their occupational characteristics and work setting using codes from the Standard Occupational Classification (SOC) system and the North American Industry Classification System (NAICS), respectively. This report presents estimates based on the 1,417 respondents in the January survey who reported working in a health-care setting or involvement in hands-on care of patients (e.g., firefighters or other first responders).

The response among sampled panelists for the January survey was 74.1%. Approximately 89% of surveys for the month were completed by January 14. Estimates reported most accurately represent vaccination status as of mid-January and are referenced as such throughout the report. Results from the survey were weighted to reflect selected demographic and geographic characteristics of the U.S. population of HCP, as reflected in the most recent monthly Current Population Study,§ and occupational characteristics measured in the screening questionnaire.¶ Statistical significance of differences was determined by chi-square test.

Seasonal influenza vaccine became available in August 2009, and 2009 H1N1 vaccine became available in October. By mid-January 2010, an estimated 61.9% of HCP had received a seasonal influenza vaccination** and an additional 3.1% reported their intent to be vaccinated by the end of the season†† (Table 1). In contrast, an estimated 37.1% of HCP had received a 2009 H1N1 vaccination,§§ and an additional 10.0% reported intent to be vaccinated by the end of the season. Coverage with any influenza vaccine (2009 H1N1 or seasonal) increased from 2.1% in August, when seasonal vaccine was first introduced, to 64.3% by mid-January (Figure). Coverage with both seasonal and 2009 H1N1 influenza vaccine was 34.7%.

Seasonal influenza vaccination coverage was substantially higher among HCP working in hospitals (71.7%) than those working in long-term care facilities (54.0%) or other settings (48.4%) (p = 0.003 and p = 0.001, respectively). 2009 H1N1 vaccination coverage also was higher among HCP working in hospitals (50.6%) than those working in outpatient clinics (39.2%), long-term care facilities (20.1%), or other settings (33.4%) (p = 0.003, p<0.001, and p = 0.015, respectively). For both vaccine types, physicians, physician assistants, dentists, and nurses had similar vaccination levels, which were slightly higher than those for allied health professionals and nonclinical staff; however, differences between these professional groups were not statistically significant (Table 1). HCP working in intensive-care, burn, or obstetric units, or around seriously ill patients¶¶ were more likely to be vaccinated than other HCP for both seasonal influenza (70.2% versus 59.0%; p = 0.026) and 2009 H1N1 (48.2% versus 33.4%; p = 0.003). HCP with a bachelor's degree or higher were more likely to be vaccinated for 2009 H1N1 compared with HCP with a high school diploma or less (41.9% versus 27.6%; p = 0.014). Educational status was not associated with receipt of seasonal influenza vaccination, nor was sex, age, or race associated with coverage of either vaccine type.

HCP were more likely to believe seasonal influenza vaccination was safe*** compared with 2009 H1N1 vaccination (80.9% versus 66.6%; p<0.001). Although HCP considered both vaccines to be protective,††† more HCP believed seasonal influenza vaccination was worth the time and expense§§§ (74.2%) than did those who believed 2009 H1N1 vaccination was worth the time and expense (62.8%; p<0.001). Unavailability of vaccine was given as a reason for nonvaccination by 7.4% of HCP not vaccinated for seasonal influenza and 17.3% of HCP not vaccinated for 2009 H1N1. The two most frequently cited reasons for nonvaccination with either vaccine were "I don't need it" and "I may experience side effects."

Seasonal influenza vaccination was reported to be required¶¶¶ by employers for 11.1% of HCP and recommended by employers for 65.4% (Table 2). An employer requirement was associated with an almost twofold higher coverage rate for seasonal influenza vaccination compared with the rate among HCP whose employers neither required nor recommended seasonal vaccination (relative risk [RR] = 1.7; p<0.001); an employer requirement was associated with a rate almost threefold higher (RR = 2.6; p<0.001).

2009 H1N1 vaccination was required by employers for 8.4% of HCP and recommended by employers for 61.8%. An employer requirement was associated with an almost eightfold higher coverage rate for 2009 H1N1 influenza vaccination compared with the rate among HCP whose employers neither required nor recommended seasonal (RR = 7.8; p<0.001); an employer recommendation was associated with a rate almost fourfold higher (RR = 3.9; p<0.001).

Reported by

KM Harris, PhD, J Maurer, PhD, RAND Corporation; CL Black, PhD, GL Euler, DrPH, CW LeBaron, MD, JA Singleton, MS, Immunization Svcs Div, AE Fiore, MD, Influenza Div, National Center for Immunization and Respiratory Diseases, TF MacCannell, PhD, Div of Healthcare Quality Promotion, National Center for Preparedness, Detection, and Control of Infectious Diseases, CDC.

Editorial Note

HCP should receive influenza vaccination to protect themselves, their families, and their patients from influenza. Vaccination has been shown to reduce illness and absenteeism caused by influenza. (1,5). During the 2009--10 influenza season, by mid-January 2010, seasonal influenza vaccination coverage among HCP was 61.9%, compared with much lower levels (49%--53%) reported for the previous season, although the results from the previous season used different survey methods (e.g., in-person interviews) (4,6). To the extent that the two estimates are comparable, the January 2010 results represent a coverage level that, for the first time, meets the Healthy People 2010 target of 60% (7). Increased attention to influenza resulting from the 2009 H1N1 pandemic might have contributed to the increase in seasonal influenza vaccination coverage. However, 2009 H1N1 vaccination coverage among HCP only reached 37.1% by January. The vaccine was not available before October 2009, and unavailability during epidemic activity might have contributed ultimately to low vaccination levels among HCP. However, only 17.3% of unvaccinated HCP listed unavailability of vaccine as a reason for nonvaccination at the time of the January survey.

Seasonal vaccination coverage was highest (71.7%) in hospital settings and among HCP who work in intensive-care, burn, or obstetric units, or around seriously ill patients (70.2%). However, coverage was lower (54.0%) in settings such as long-term care facilities, where medically fragile patients could be at increased risk if exposed to influenza viruses. The results for long-term care facilities likely indicate that programs to educate HCP working in such facilities about the safety, effectiveness, and public health importance of influenza vaccines have not resulted in adequate coverage.

The results from this survey indicate that HCP who were subject to employer requirements for vaccination were more likely to be vaccinated compared with those not subject to such requirements. Although this association by itself cannot establish a causal link, it suggests that the requirements helped boost coverage. In previous studies, coverage levels of 88%--98% have been reported from health-care institutions that have required annual vaccination for seasonal influenza as a condition for employment (8,9). Health-care administrators should 1) consider the level of vaccination coverage among HCP to be one measure of patient safety and quality assurance, 2) track coverage levels by ward, unit, and occupation, and 3) determine the factors that helped raise seasonal influenza vaccination coverage and build on these increases for the next season (1).

The findings in this report are subject to at least three limitations. First, all results are based on self-reported influenza vaccination. Because of the limited sample size, confidence limits around some estimates are large and, because this is an interim analysis, final estimates might differ. Second, the survey possibly is subject to selection bias, if participation in the survey is correlated with receipt of vaccination. Vaccination coverage also could have been affected by unmeasured confounders, so causal inference about factors associated with vaccination should be made with caution. Finally, the definition of HCP used in this survey might vary slightly from definitions used in previously published surveys of vaccination coverage.

To further assess strategies for increasing vaccination coverage among HCP, longitudinal surveillance of seasonal influenza vaccination among HCP was initiated through CDC's National Healthcare Safety Network (NHSN)**** in September 2009. Enrolled health-care facilities are able to enter yearly individual-level vaccination data, including statements of declination among facilities opting for mandatory influenza vaccination. With increases in enrollment, NHSN might be able to provide national estimates for yearly vaccine coverage among HCP, identify undervaccinated HCP groups, and target appropriate interventions to increase coverage (10).

References

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