In Canada the National Advisory Committee on Immunization has set a 90% target vaccination rate for people aged 65 years or older or at high risk of influenza-related complications.8
Furthermore, in a closed setting such as a long-term care facility, it is recommended that at least 80% of the residents and staff be vaccinated to achieve herd immunity.5
Our data suggest that, although influenza vaccination rates among residents and staff of Canadian long-term care facilities have increased over the last decade, they remain suboptimal. In the facilities responding to our survey, 83% of the residents were vaccinated for the 1998/99 influenza season. Several pieces of evidence suggest that this is an overestimate of the true rate. Validation of the 1991 survey data by chart review found lower than reported rates (by 7% and 30%) in 2 of 12 facilities.13
A recent audit of 7 facilities in Ontario with influenza outbreaks in 1999/2000 revealed that vaccination rates among residents measured by chart review were a median of 2% (range 0%–7%) lower than the rates reported to the provincial ministry of health (unpublished data). In addition, survey response rates were higher in provinces with higher overall vaccination rates, which suggests that the vaccination rates in the nonresponding facilities may have been lower than those in the facilities that responded to the survey. In summary, these data suggest that the overall influenza vaccination rate among residents in Canadian long-term care facilities remains below 80%. This, combined with the fact that there was a mean staff:resident ratio of 1.1 and that only 40% of staff were vaccinated for the 1998/99 season, substantially explains why there is inadequate herd immunity against influenza in our long-term care facilities.
Staff vaccination against influenza is important because staff can transmit influenza to residents. The estimated efficacy of the vaccine in preventing illness in staff is as high as 88%,4,15,16,17
with benefits including lower rates of influenza-like illness and complications, fewer physician visits and lost work days, and decreased antibiotic use.15,16,17,18,19
Two randomized controlled trials have shown that staff vaccination reduces influenza-related morbidity and death among facility residents.20,21
Our findings suggest that the risk of influenza outbreaks is substantially reduced in facilities with higher staff vaccination rates. The apparently greater effect of vaccination among staff and residents in smaller facilities than in larger ones may be because the absolute number of susceptible people is important, or it may be due to lack of power to detect a difference within subgroups (e.g., only 5 of 101 facilities with more than 100 beds reported staff vaccination rates greater than 75%).
The variation in staff vaccination rates among provinces suggests that provincial policies have a substantial impact on vaccine use,12
although the small numbers of facilities in some provinces suggests that these results be interpreted with caution. The impact of provincial public health policies was clearly demonstrated in 1999 in Ontario. The Ontario Ministry of Health and Long-Term Care began paying for influenza vaccine for staff in long-term care facilities in 1993. In the fall of 1999, the ministry issued an influenza prevention and surveillance protocol that recommended policies restricting unvaccinated staff from work during outbreaks unless they were taking antiviral prophylaxis. The policy recommendation, and its enforcement by some local public health units, resulted in an increase in median staff vaccination rates, from 45% in 1998/99 to 86% in 1999/2000 (Ontario Ministry of Health and Long-Term Care: unpublished data).
Pneumococcal vaccination increased substantially over the last decade, but this vaccine remains underused compared to influenza vaccine, and pneumococcal vaccination rates among elderly people in Canada are significantly lower than those in the United States.22,23
The low rates are associated with physician doubts about the vaccine's effectiveness.24,25,26,27,28,29
However, there is good evidence that vaccination is associated with significant protection against bacteremic pneumococcal disease and that its use reduces costs to the health care system.30,31,32
Currently, the National Advisory Committee on Immunization recommends that the pneumococcal vaccine be given to all residents of long-term care facilities who have not been previously vaccinated.8
Our findings showed that vaccination rates among residents were higher in facilities with an infection control practitioner, those with a higher than average number of physicians physicians and those in provinces with established, publicly funded pneumococcal vaccination programs. Infection control practitioners likely influence rates through their promotion of preventive practices. Facilities with such individuals also reported higher resident and staff influenza vaccination rates and increased use of amantadine. An increased number of physicians might increase the probability that at least one will promote vaccination. The effect of publicly funded programs re-emphasizes the importance of public health programs in promoting vaccination.
The National Advisory Committee on Immunization recommends that amantadine prophylaxis be offered to all asymptomatic residents for the duration of an influenza A outbreak.8
Amantadine is 60%–90% effective in preventing influenza in exposed individuals,8,33
and although there are no randomized controlled trials of outbreak control, experience suggests that mass amantadine prophylaxis is usually very effective in controlling outbreaks.34,35,36,37
The reported failure rate of amantadine identified in our survey is similar to that reported by Tamblyn.38
Reasons for failure could include suboptimal dosing regimens, mixed outbreaks involving influenza and noninfluenza viruses or the emergence of amantadine-resistant strains of influenza virus, a phenomenon estimated to occur in up to 30% of amantadine-treated patients.39
A better understanding of the reasons for failure is important in determining how outbreak control can be improved. The fact that a median of 22 residents were involved in outbreaks controlled with amantadine highlights another problem in influenza management: early detection of outbreaks. Gomolin and associates40
have suggested that a cluster of 3 ill residents on a unit within 72 hours deserves investigation. If outbreaks were consistently detected at this point, and amantadine prophylaxis started promptly, the median number of involved residents should be no more than 10.
Prior studies have identified rates of adverse events associated with amantadine use as high as 47%,34
and the proportion of residents who stopped taking amantadine because of side effects has ranged from 7%–19%.34,41,42,43
Most of these studies used amantadine doses of 100 mg/d. In our study, a majority of the facilities measured creatinine clearance to determine individual doses, a practice recommended by the National Advisory Committee on Immunization and one that has been shown to reduce the incidence of side effects.44
Although we did not collect data on overall rates of side effects, only 3% of the residents were reported to have stopped taking amantadine because of adverse effects, which emphasizes that amantadine prophylaxis in this setting poses a lesser risk than exposure to influenza. It is unclear how usage patterns will change with the advent of neuraminidase inhibitors, which are active against both influenza A and B, have a lower incidence of side effects and have less potential for the emergence of resistance.45
In summary, our study shows that influenza and pneumococcal vaccination rates in Canadian long-term care facilities have risen over the last decade but remain suboptimal. Vaccination of both staff and residents appears to be important in preventing influenza outbreaks, and the use of mass antiviral prophylaxis is effective in controlling outbreaks when they do occur. Our data explain why the National Advisory Committee on Immunization now states that “healthcare workers and their employers have a duty to actively promote, implement and comply with influenza immunization.”12
These data should also encourage all those responsible for the care of residents in long-term care facilities, and for the accreditation and regulation of such facilties, to establish, support and expand vaccination programs and antiviral prophylaxis policies in order to reduce the impact of influenza and pneumococcal pneumonia in this fragile population.