The effectiveness of influenza vaccine against influenza a (H3N2) virus infections in nursing homes in Niigata, Japan, during the 1998-1999 and 1999-2000 seasons.
OBJECTIVE
To evaluate the effectiveness of influenza vaccines against influenza-like illness (ILI) among nursing home residents.


METHODS
Prospective, nonrandomized, cohort study.


METHODS
Nine nursing homes during the 1998-1999 influenza season and 11 nursing homes during the 1999-2000 influenza season in Niigata Prefecture, Japan.


METHODS
Six hundred ninety-nine residents and 440 healthcare workers (HCWs) during the first season, and 930 residents and 517 HCWs during the second season, with vaccination rates ranging from 0% to 97.7%.


RESULTS
Overall, ILI decreased from 24.3% during the 1998-1999 season to 8.8% during the 1999-2000 season. Multivariate analysis adjusted for several factors, including gender, age, underlying diseases, and resident and HCW vaccination rates, failed to demonstrate clear individual protection of residents (relative risk [RR], 1.42; P = .2 for the first season; RR, 0.95; P = .9 for the second season). However, vaccination rates of 60% or greater for residents and HCWs reduced the risk of ILI, and also could prevent outbreaks during the 2 seasons. Highly impaired activities of daily living and chronic respiratory diseases were significantly associated with increased ILI.


CONCLUSIONS
A high vaccination rate for both residents and HCWs may reduce the risk of ILI and institutional outbreaks in nursing homes.
Saito
Reiko
R
Department of Public Health, Niigata University School of Medicine, Niigata City, Japan.
Suzuki
Hiroshi
H
Oshitani
Hitoshi
H
Sakai
Takatsugu
T
Seki
Nao
N
Tanabe
Naohito
N
D000368:Aged; D000369:Aged, 80 and over; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype; D009980:Influenza A virus / Q000302:isolation & purification*; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D007564:Japan / Q000453:epidemiology; D008297:Male; D009735:Nursing Homes; D011446:Prospective Studies; D018571:Sentinel Surveillance; D016896:Treatment Outcome
D007252:Influenza Vaccines