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Mandatory flu shots: Is science strong enough?
APIC cites 'ethics,' AOHP says 'science'
Everyone agrees that health care workers should receive the influenza vaccine each year to protect themselves and their patients. But the call for mandatory policies relies on the premise that gaps in vaccination jeopardize vulnerable patients. Although a number of studies are widely cited to support mandatory vaccination, there is actually little evidence of the impact of flu vaccination in hospitals.
As momentum grows for mandatory vaccination, OHM examined major studies and spoke to experts to assess some common assertions made about influenza vaccination of health care workers. Emotions run high on this issue, which is framed either as an imperative to "do no harm" or an unnecessary coercion with limited benefit.
"The science at best weakly supports voluntary vaccination of nursing home staff, achieving a goal rate in the 40% to 70% range," says Melanie Swift, MD, medical director of the Vanderbilt Occupational Health Clinic at Vanderbilt University in Nashville, TN. "I think to extrapolate any benefit in the acute care setting beyond that is not supported by the evidence."
Swift, who is vice chair of the Medical Center Occupational Health Section of the American College of Occupational and Environmental Medicine (ACOEM), notes, "We already have a vaccination rate in acute care hospitals that meets or exceeds that [level achieved] in all of the studies."
Infection preventionists support mandatory vaccination as the way to catapult rates from about 62% of health care workers to close to 100%.
The rates from voluntary programs simply aren't high enough, says Linda Greene, RN, MPS, CIC, director of infection prevention at the Rochester (NY) General Health System. "What we're looking at is the ethical responsibility to protect those who are most vulnerable. We really felt that was a very strong message we needed to bring forth to our health care workers," says Greene, who was lead author of the position paper of the Association for Professionals in Infection Control and Epidemiology (APIC).
In February, APIC became the most recent infection control organization to support mandatory programs: "As a profession that relies on evidence to guide our decisions and actions, we can no longer afford to ignore the compelling evidence that supports requiring influenza vaccine for [health care personnel]. This is not only a patient safety imperative, but is a moral and ethical obligation to those who place their trust in our care."1
However, occupational health professionals, as a group, have not supported mandatory policies. The Association for Occupational Health Professionals in Healthcare (AOHP) issued a statement emphasizing the importance of health care worker vaccination but opposing the policies that require vaccination as a condition of employment: "AOHP respects the individual [health care worker's] right to make an informed decision regarding accepting or declining the influenza vaccine."
ACOEM also has declined to endorse mandatory programs: "Current evidence regarding the benefit of influenza vaccination in HCW as a tool to protect patients is inadequate to override the worker's autonomy to refuse vaccination," ACOEM said in its guidance statement.2
Examining the evidence
Here are some of the assertions about flu vaccination of health care workers and the scientific basis:
Low vaccination rates of health care workers are associated with higher rates of mortality among patients: The evidence that influenza vaccination reduces the risk of mortality among patients or residents comes from long-term care facilities and is relatively weak. In one often-cited article from 1997, mortality rates declined in British long-term care facilities in which health care workers were offered vaccine. (Sixty-one percent of them were vaccinated.)
However, there was very little laboratory-confirmed Influenza: 6 of 107 in patients in the staff-unvaccinated group and 5 of 118 in the staff-vaccinated group. The authors noted that some elderly people do not have a rise in antibody titer after influenza vaccination or perhaps after influenza infection which may have resulted in an undercount of influenza cases. Other respiratory illnesses were circulating as well and were detected in the study population. The authors cautioned, "...we do not have any direct evidence that the reduction in rates of patient mortality and influenza-like illness that were associated with HCW vaccination were due to prevention of influenza."3
Other studies have shown effects on mortality in long-term care, with caveats. In one, vaccination of caregivers (51% vaccinated) was associated with overall lower mortality but not lower rates of non-fatal influenza infection.4 A 2009 study found that doubling the vaccination rate of health care workers (32% to 70%) did not produce a statistically significant difference in mortality although an analysis that adjusted for other possible contributors to mortality did show an impact from vaccination.5
A Cochrane Review of five studies on influenza vaccination among health care workers in long-term care (including the three cited here) found that "all [are] at high risk of bias....We conclude there is no evidence that vaccinating HCWs prevents influenza in elderly residents in long-term care facilities."
Overall, influenza infection causes less than 10% of mortality in people 60 years of age or older, the Cochrane authors noted. Future studies should test for the impact of a variety of interventions, including hand-washing, mask use, quarantine of ill patients/residents, and restriction of visitors, they said.6
Increasing vaccination rates reduces nosocomial transmission of influenza. There have been few studies of nosocomial transmission of influenza in hospitals, and they include other variables that make it difficult to assess the impact of vaccination. A widely cited 2004 study at the University of Virginia Health System found that the proportion of nosocomial flu cases to community-acquired cases among hospitalized patients dropped over 12 years (in 13 influenza seasons), while health care worker vaccination increased. The overall number of nosocomial cases varied, but averaged about 4 cases per year. (It was zero in 1994-95, 1995-96, and 1999-2000, the final season of the study.) Community cases also varied but spiked in the last years of the study. The peak vaccination rate of health care workers was 67%.
Although other infection control interventions also were used to prevent nosocomial spread, the authors concluded that the change over time could be attributed to the rise in vaccination.7
A recent French study found patients had an increased risk of a health care-associated influenza-like illness (ILI) if they were exposed to a health care worker with ILI but the risk was even greater if they were exposed to a patient with ILI and greatest with exposures to both a patient and health care worker who were sick. Only 20% of the ILI cases were laboratory-confirmed influenza. The study was not designed to detect the protective effect of influenza immunization.8
Interestingly, a recent German study did not find that health care workers were at increased risk of influenza because they worked in an acute care facility. The greatest risk: Having children in their home. Most (74%) of the ILI was not influenza, and 30% of the lab-confirmed influenza was asymptomatic.9
Mandatory vaccination results in lower absenteeism. Studies have found only a modest impact on health care worker absenteeism. The flu vaccine varies in effectiveness, and influenza typically causes only a small portion of the respiratory illness seen each winter.
But there's one other reason: Health care workers often come to work sick. One study of hospital-based physicians, nurses and respiratory therapists found a lower amount of absenteeism and febrile respiratory illness in the vaccinated group, but the results weren't statistically significant. "The health care professionals in our study seem unlikely to be absent from work even when they experience a febrile respiratory illness," the authors noted.10
Virginia Mason Medical Center, the first hospital to require flu vaccination as a condition of employment, achieved vaccination rates above 98% but wasn't able to demonstrate a significant impact on absenteeism.11 There are simply too many variables, notes Joyce Lammert, MD, PhD, chief of the Department of Medicine. For example, employees may take leave to stay home with a sick child, or there may be other diseases, such as norovirus, circulating in the community.
A mandatory program greatly increases the proportion of health care workers who receive the vaccine. There is no question that a mandatory policy produces almost universal health care worker vaccination. When Virginia Mason implemented the policy in 2005, the vaccination rate rose from 29.4% (a low rate in 2004 due to supply shortages) to 97.6%. The rates have since been above 98%.
When BJC Healthcare in St. Louis implemented a mandatory policy, vaccination rates rose from 71% in 2007 to 98.4% in 2008. The health system granted medical exemptions to 321 employees and religious accommodations to 90 employees, and eight employees were terminated for failing to comply with the policy.12
In a survey conducted by the RAND Corp. for the Centers for Disease Control and Prevention, 21% of hospital workers reported that their employers have a flu vaccination requirement. Overall among health care workers in various settings, flu mandates led to a vaccination rate of 97.6% compared with 64.5% when employers recommended the vaccine.
1. Greene LR, Cox T, Dolan S, et al. APIC position paper: Influenza vaccination should be a condition of employment for healthcare personnel, unless medically contraindicated. Association for Professionals in Infection Control and Epidemiology, Washington, DC. January 27, 2011. Available at www.apic.org/Content/NavigationMenu/GovernmentAdvocacy/PublicPolicyLibrary/APIC_Influenza_Immunization_of_HCP_12711.PDF. Accessed on February 21, 2011.
2. Swift MD, Buchta WG, Russi M, et al. Seasonal influenza prevention in health care workers. American College of Occupational and Environmental Medicine, Elk Grove Village, IL. November 17, 2008. Available at www.acoem.org/guidelines.aspx?catID=3. Accessed on February 21, 2011.
3. Potter J, Stott DJ, Roberts AG, et al. Influenza vaccination of health care workers in long-term-care hospitals reduces the mortality of elderly patients. J Infect Dis 1997;175:1-6.
4. Carman WF, Elder AG, Wallace LA, et al. Effects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: a randomized controlled trials. Lancet 2000;355:93-97.
5. Lemaitre M, Meret T, Rothan-Tondeur M, et al. Effect of influenza vaccination of nursing home staff on mortality of residents: a cluster-randomized trial. Jrl Amer Geri Soc 2009;57:1580–1586.
6. Thomas RE, Jefferson T, Lasserson TJ. Influenza vaccination for healthcare workers who work with the elderly. Cochrane Database of Systemic Reviews 2010; 2:CD005187. Available at www.thecochranelibrary.com/userfiles/ccoch/file/CD005187.pdf. Accessed on February 7, 2011.
7. Salgado CD, Giannetta ET, Hayden FG, Farr BM. Preventing nosocomial influenza by improving the vaccine acceptance rate of clinicians. Infect Control Hosp Epidemiol 2004;25:923-928.
8. Vanhems P, Voirin N, Roche S, et al. Risk of influenza-like illness in an acute health care setting during community influenza epidemics in 2004-2005, 2005-2006, and 2006-2007: A prospective study. Arch Intern Med 2011;171:151-157.
9. Williams CJ, Schweigher B, Diner G, et al. Seasonal influenza risk in hospital healthcare workers is more strongly associated with household than occupational exposures: results from a prospective cohort study in Berlin, Germany, 2006/07. BMC Infect Dis 2010; 10:8. Available at www.ncbi.nlm.nih.gov/pmc/articles/PMC2836320/. Accessed on February 7, 2011.
10. Wilde JA, McMillan JA, Serwint J, et al. Effectiveness of influenza vaccine in health care professionals. JAMA 1999; 281:908-913.
11. Rakita RM, Hagar BA, Crome P, and Lammert JK. Mandatory influenza vaccination of healthcare workers: A 5-year study. Infect Control Hosp Epidemiol 2010;31:881-888.
12. Babcock HM, Gemeinhart N, Jones M, et al. Mandatory Influenza Vaccination of Health Care Workers: Translating Policy to Practice. Clin Infect Dis 2010;50:459-464.