The importance of influenza immunizations for health-care workers

Introduction
The National Advisory Committee on Immunization (NACI) recommends that all institutionalized persons, all persons 65 years of age and older, and certain persons with chronic health problems be vaccinated yearly against influenza.[1] Canada, along with at least 10 other developed countries, also recommends immunization for health-care workers.[1,2] A distinct recommendation to health-care workers has been made yearly by NACI since 1986, and in British Columbia, influenza vaccine has been provided free to health-care workers for several years.

Immunization of health-care workers is advised as a strategy to reduce the carriage and transmission of influenza. Published data show that infected staff spread influenza among patients, causing a variety of ill effects, including hospitalization and death.[3,4] Studies have shown that up to 25% of health-care workers are infected with influenza during the winter months[5] and those that are acutely ill seldom stay away from work.[6] Up to one-half of influenza infections in adults are sub-clinical and even those who are asymptomatic can shed virus and transmit it to others. In this way, staff can introduce influenza and perpetuate its transmission within facilities, placing vulnerable patients at risk.[7]

A Canada-wide survey of long-term care facilities in 1990 showed that almost 80% of residents were immunized with influenza vaccine[8] and BC estimates are comparable. Although it is estimated that resident vaccination rates of at least 70% to 80% are needed to provide protection against outbreaks, facility outbreaks have occurred where coverage levels have exceeded this.[8-11]

Local rates not high enough
Of all groups to whom NACI recommends influenza vaccination, uptake by health-care workers remains steadfastly among the lowest. In the Canada-wide survey of 1990 only 19% of facilities reported staff vaccination rates above 25%[8], and in BC, overall staff uptake has typically been below 30%. A 1998–99 systematic review of uptake among staff of long-term care facilities in two Lower Mainland regions confirms this. The initial year of enhanced staff promotion in one of the regions achieved improvement over historical coverage estimates of <20% for that region. However, uptake in both regions during 1998–99 was still only 37%. Of concern, information from one of the regions showed that those providing direct patient care were no more likely than other staff to be immunized. In a separate survey of staff in 12 select facilities within these regions, 20% of respondents indicated they work in more than one facility, placing patients in multiple settings at potential risk (authors’ unpublished data, 1999).

Provincial targets aim for 90% of residents and staff of long-term care facilities to be immunized against influenza. Current estimates that fall far below this are disturbing. This is particularly true in light of more recent evidence proving the critical role of workers in protecting their high-risk patients. A pivotal study by Potter et al. in 1997 shifted emphasis from resident to staff immunization. In this study, worker vaccination coverage above 60% made a substantial difference in reducing mortality among long-term care patients (41% relative risk reduction). When patients were not vaccinated, vaccination of health-care workers resulted in fewer patient deaths from all causes. Even when patients were vaccinated, settings with vaccinated health-care workers had fewer patient deaths than settings with unvaccinated staff.[12] This finding has since been corroborated in other settings. It is now clear that influenza vaccination of health-care workers substantially reduces the risk of mortality in elderly patients of long-term care, probably through prevention of nosocomial transmission.[13]

Studies have shown that employees themselves derive benefit from influenza immunization in terms of reduced sick days and absenteeism with a range of 20% to 70% reduction in work loss days due to respiratory illness.[14-16] Nichol et al demonstrated a 25% reduction in episodes of self-reported upper respiratory illness, 43% reduction in sick leave due to all upper respiratory illness, and 44% reduction in doctor’s office visits for upper respiratory illness among the vaccinated, with an overall 0.5-day reduction in absenteeism per vaccinee.[15] Estimates of cost savings attributed to influenza vaccination have varied. Yassi et al showed a net benefit, measured as the value of sick time avoided compared with costs, of about $40 per vaccinated employee.[17]

Why the poor uptake?
Various studies have assessed the factors associated with vaccine acceptance by health care staff.[18-23] Approximately 45% of health-care staff in one survey cited fear of developing influenza from the vaccine as the reason they had not received it.[18] Since the vaccine contains only killed inactivated influenza virus, this is not possible. Other frequently cited barriers include ambivalence about the disease, doubts about efficacy, and fear of short- or long-term side effects.

Vaccine has repeatedly been shown to have good efficacy (70% to 90%) against laboratory-confirmed illness in healthy young adults when there is good match between the circulating strains and vaccine components, with lower protection (40% to 60%) when there is mismatch.[16] Concerns related to side effects are largely unfounded. Recent placebo-controlled trials have confirmed that systemic symptoms such as fever, headache, and malaise do not occur more often following vaccination with split-virus vaccines, currently used in BC, than after placebo.[16,24] Local symptoms such as arm redness and soreness are more often experienced following vaccination but they are generally mild and do not interfere with daily activities.[16,24] Plain acetaminophen from the time of vaccination and every 4 hours for 4 doses significantly reduces the incidence of sore arm following whole-virus vaccination.[25]

During the 1998–99 influenza season, two Lower Mainland health regions systematically assessed staff attitudes towards influenza immunization in 12 of the 67 long-term care facilities within their regions. Of 1100 staff surveyed, half (10% of all staff in the two regions) responded to a questionnaire about predictors, beliefs, and behaviors. Nearly 40% of respondents indicated they had never received influenza immunization. The mean duration of employment in long-term care was 10 years.

In this survey, those who did not receive vaccine during the 1998–99 season (43%) most often cited fear of side effects (31%), fear of getting influenza from the vaccine (22%), and lack of concern about influenza (24%) as the reason. Approximately 20% felt that it was not needed. Personal need appeared to affect uptake—more than 10% of all respondents had other at-risk eligible conditions, and uptake among this group was substantially higher at 75%.

Correcting the problem
Those who did not get vaccinated indicated that more information about efficacy (30%) and safety (26%) or recommendation from their physician (19%) would encourage them to receive vaccine next season. Almost 30% indicated they would get vaccinated if it were a mandatory requirement of employment (authors’ unpublished data, 1999).

Studies suggest that intensive campaigns can improve staff immunization uptake.[22,23] Scheifele et al[26] reported an acceptance rate greater than 50% among hospital employees with promotional activities that included not only general notices but also individual memos and information meetings. Recent efforts in BC have attempted to address concerns most often cited by health-care workers. The accompanying fact sheet can be used by health-care workers in encouraging colleagues and employees to participate in protecting themselves and their patients.

Across Canada, increasing focus and more stringent efforts are being directed toward improving health-care staff immunization. Efforts in some jurisdictions have included region-wide competitions and specific facility comparisons conducted through local media. In Ontario, a recent Labor Relations Board hearing addressed the collective grievance of unvaccinated employees who refused prophylaxis and were excluded without pay from the setting of a nursing home outbreak. The board found in favor of the facility, citing protection of frail residents as justifiable cause. Mandatory staff influenza immunization was also the jury’s first recommendation in a recent Ontario coroner’s inquest addressing the influenza-related deaths of residents during a facility outbreak. It is likely that such restrictive measures will be endorsed more broadly across Canada as evidence mounts showing failure to protect health-care workers places the patients in their care at risk.

Protect yourself and your patients--get an annual flu shot

Dr Danuta Skowronski is a physician epidemiologist with Epidemiology Services, BC Centre for Disease Control. Dr Robert Parker is the associate medical health officer with Simon Fraser Health Region. At the time of writing, Dr Robert Strang was an associate medical health officer with South Fraser Health Region (he is now the medical health officer in Halifax).