28 September 2012
Vaccination of Health Care Workers to Protect Patients at Increased Risk for Acute Respiratory Disease
Dolan P.G. et al in their paper Vaccination of health care workers (HCW) to protect patients at increased risk for acute respiratory disease (1) , review all available studies in order to examine the effectiveness of vaccinating health care workers to indirectly protect patients at risk of severe or complicated disease after acute respiratory infections. The authors of this study used standardized tools to search and reviewed articles in health care databases and gray literature. Twenty citations met the inclusion criteria, all considering influenza vaccination and most of them were conducted in long-term residential care settings. From these studies it was difficult to specifically isolate the effect of HCW vaccination from other factors that may influence patient outcomes such as patient vaccination and actual influenza infection. Other confounding factors such as organizational culture and workplace practices were also acknowledged. However, across different outcome measures there was a consistent trend towards an indirect protective effect for patients when HCW were vaccinated in long term care facilities. There was not enough evidence to confidently extrapolate this to other at-risk patient groups.
It has long been argued that Health Care Workers should be vaccinated in order to prevent transmission of influenza to their vulnerable patients. However, evidence supporting this practice remains limited. It is estimated that approximately 20% of HCW are infected with influenza each season (2). Additionally, it has been shown in surveys that HCW often come to work even when suffering from symptoms of respiratory infections (3). Individuals who are at highest risk for developing complications from influenza include people over 65 years of age, and those with chronic underlying health problems are more at risk of severe or complicated respiratory illness after infection compared to the general population (4). These groups of people are also more likely to frequent health care settings and outbreaks have been reported in a number of high risk environments such as acute care (5,6), pulmonary wards (7) and in nursing homes (8,9). In addition, these same individuals respond less well to vaccination, increasing the importance of preventing infection through other means such as avoidance and vaccination of close contacts. The WHO, in accordance with the SAGE recommendations on immunization, recommends seasonal influenza vaccination of HCW to provide protection against the individual as well as reducing the spread of influenza to vulnerable patient groups (9). Case control studies, although the best type of study for vaccine efficacy evaluation, do have methodological constraints (5,6). Bias and confounding in case-control studies have the potential to skew VE estimates and hence these studies should be generally viewed with caution. Kissling & Valenciano identify such methodological constraints and attempt to alleviate them by collecting extensive data on confounders and controlling for specific factors (1). Due to the detections of influenza A(H3N2) in the temperate region of the southern hemisphere, this study of vaccine efficacy has particular relevance for countries experiencing influenza A(H3N2) transmission. In the northern hemisphere 2011/12 influenza season, A(H3N2) drift was identified during the season, potentially contributing to lower VE (7). Studies such as Kissling & Valenciano’s provide much needed monitoring of vaccine efficacy, assisting seasonal vaccine strategy decisions. Regular and accurate surveillance data is the best tool available to better provide for informed decisions on strategies for seasonal vaccination. Until a universal vaccine is developed, surveillance continues to be important in monitoring of the seasonal changes of influenza viruses and the vaccine strains selection process. Influenza vaccine effectiveness against influenza viruses varies among populations and is highly dependent on matching vaccines to circulating viruses. Vaccine efficacy studies provide valuable insights into these variances in sub-populations. Due to seasonal changes of influenza viruses, the WHO advises on vaccine strains for the northern and southern hemispheres and recommends annual influenza vaccination for populations at-risk for severe infections. Even vaccinated, individuals with chronic medical conditions should seek early treatment when ill with ILI symptoms if influenza virus circulation is known in the community.
1) Dolan GP, Harris RC, Clarkson M, Sokal R, Morgan G, Mukaigawara M, Horiuchi H, Hale R, Stormont L, Béchard-Evans L, Chao YS, Eremin S, Martins S, Tam JS, Peñalver J, Zanuzadana A, Nguyen-Van-Tam JS. Vaccination of health care workers to protect patients at increased risk for acute respiratory disease. Emerg Infect Dis. 2012 Aug;18(8):1225-34
2) Elder AG, O’Donnell B, McCruden EAB, Symington IS, Carman WF. Incidence and recall of influenza in a cohort of Glasgow healthcare workers during the 1993-4 epidemic: results of serum testing and questionnaire. BMJ. 1996;313:1241-2.
3) CDC. Influenza Vaccination of Health-Care Personnel, Recommendations of the Healthcare Infection Control Practices Advisory Committee (HICPAC) and the Advisory Committee on Immunization Practices (ACIP). MMWR 2006;55(RR-2):1-16.
4) Jefferson T, Di Pietrantonj C, Rivetti A, Bawazeer GA, Al-Ansary LA, Ferroni E. Vaccines for preventing influenza in healthy adults. Cochrane Database of Systematic Reviews 2010, Issue 7. Art. No.: CD001269. DOI: 10.1002/14651858.CD001269.pub4
5) World Health Organisation. WHO guidelines for pharmacological management of influenza. Revised February 2010. Part 1: recommendations (accessed 2012 September 5). http://www.who.int/csr/resources/publications/swineflu/h1n1_guidelines_pharmaceutical_mngt.pdf
6) Weingarten S, Friedlander M, Rascon D, Ault M, Morgan M, Meyer RD. Influenza surveillance in an acute-care hospital. Arch Intern Med. 1988;148:113-6.
7) Jaconmo V, Sartor C, Zandotti C, Atlan-Gepner C, Drancourt M. Nosocomial influenza outbreak in an intensive-care unit. Med Mal Infect. 2001;31:563-8.
8) Rivera M, Gonzalez N. An influenza outbreak in a hospital. Am J Nurs. 1982;82:1836-8.
9) Strausbaugh LJ, Sukumar SR, Joseph CL. Infectious disease outbreaks in nursing homes: an unappreciated hazard for frail elderly persons. Clin Infect Dis. 2003;36:870-6.
10) Nuorti JP, Butler JC, Crutcher JM, Guevara R, Welch D, Holder P, et al. An outbreak of multi drug resistant pneumococcal pneumonia and bacteremia among unvaccinated nursing home residents. N Engl J Med. 1998;338:1861-8.
11) Meeting of the Strategic Advisory Group of Experts on immunization, April 2012- conclusions and recommendations, WER, 2012, No. 21, 87,201-216