Outbreaks of influenza A and B in a highly immunized nursing home population.
BACKGROUND
Large outbreaks of influenza A and B may occur in nursing homes despite high resident vaccination rates, even when the vaccine strain is matched to the circulating strain. This study reports the occurrence of separate influenza A and B outbreaks in a nursing home where more than 85% of residents were vaccinated.


METHODS
Prospective surveillance was used to identify symptomatic residents in a rural Wisconsin nursing home with 680 residents. Viral cultures were obtained from all consenting residents identified with new respiratory symptoms even in the absence of temperature elevation. A "case" refers to a resident with a respiratory illness and an influenza isolate.


RESULTS
During the 1992-93 season, 86% of 670 total residents were vaccinated, 104 (15.5%) were cases with influenza B. During the 1993-94 season, 89% of 690 total residents were vaccinated, 68 (9.8%) were cases with influenza A. The antigenic matches between vaccine and epidemic strains were characterized as "identical or minimal difference" by the Centers for Disease Control and Prevention.


CONCLUSIONS
There is still a need to protect residents from infectious secretions and for contingency plans to permit the rapid use of antiviral agents. Future efforts are needed to develop vaccines that provide greater protection and to improve staff vaccination rates.
Drinka
P J
PJ
Wisconsin Veterans Home, USA.
Gravenstein
S
S
Krause
P
P
Schilling
M
M
Miller
B A
BA
Shult
P
P
D000368:Aged; D000369:Aged, 80 and over; D000547:Amantadine / Q000627:therapeutic use; D000998:Antiviral Agents / Q000627:therapeutic use; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000150:complications / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D009735:Nursing Homes; D009975:Orthomyxoviridae; D011159:Population Surveillance; D011446:Prospective Studies; D012299:Rimantadine / Q000627:therapeutic use; D014611:Vaccination / Q000706:statistics & numerical data; D014922:Wisconsin / Q000453:epidemiology
D000998:Antiviral Agents; D007252:Influenza Vaccines; D012299:Rimantadine; D000547:Amantadine