The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial.
OBJECTIVE
To determine the efficacy of influenza vaccination in elderly people.


METHODS
Randomized double-blind placebo-controlled trial.


METHODS
Fifteen family practices in the Netherlands during influenza season 1991-1992.


METHODS
A total of 1838 subjects aged 60 years or older, not known as belonging to those high-risk groups in which vaccination was previously given.


METHODS
Purified split-virion vaccine containing A/Singapore/6/86(H1N1), A/Beijing/353/89(H3N2), B/Beijing/1/87, and B/Panama/45/90 (n = 927) or intramuscular placebo containing physiological saline solution (n = 911).


METHODS
Patients presenting with influenzalike illness up to 5 months after vaccination; self-reported influenza in postal questionnaires 10 weeks and 5 months after vaccination; serological influenza (fourfold increase of antibody titer between 3 weeks and 5 months after vaccination).


RESULTS
The incidence of serological influenza was 4% in the vaccine group and 9% in the placebo group (relative risk [RR], 0.50; 95% confidence interval [CI], 0.35 to 0.61). The incidences of clinical influenza were 2% and 3%, respectively (RR, 0.53; 95% CI, 0.39 to 0.73). The effect was strongest for the combination of serological and clinical influenza (RR, 0.42; 95% CI, 0.23 to 0.74). The effect was less pronounced for self-reported influenza.


CONCLUSIONS
In the elderly, influenza vaccination may halve the incidence of serological and clinical influenza (in periods of antigenic drift).
Govaert
T M
TM
Department of General Practice, University of Limburg, Maastricht, The Netherlands.
Thijs
C T
CT
Masurel
N
N
Sprenger
M J
MJ
Dinant
G J
GJ
Knottnerus
J A
JA
D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000096:biosynthesis; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000276:immunology; D009981:Influenza B virus / Q000276:immunology; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000175:diagnosis / Q000517:prevention & control*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012306:Risk; D011795:Surveys and Questionnaires
D000914:Antibodies, Viral; D007252:Influenza Vaccines