BACKGROUND: According to common recommendations, influenza vaccination should be performed annually. It has been suggested that vaccination in previous years reduces vaccine efficacy in the long term. OBJECTIVE: To determine whether the protection of influenza vaccine decreases when vaccination is repeated annually. METHODS: Articles published between 1966 and 1997 were selected from MEDLINE. The end point for field studies was the influenza-related morbidity or mortality during influenza outbreaks (resulting in field protection rates). The end point for serologic studies was exceeding a protective postvaccination hemagglutination-inhibition titer (serologic protection rates). Protection rate differences between groups with single and multiple vaccinations were subjected to meta-analysis. RESULTS: Seven field studies (including 13 trials) supported the hypothesis that protection in multiple-vaccination groups is at least as good as that in single-vaccination groups. Ten trials with 5117 observations could be subjected to meta-analysis. The pooled protection-rate difference was close to 0 (1.1%; 95% confidence interval, -0.2% to 2.4%), thus detecting no difference between single or multiple vaccination. Twelve serologic studies (including 53 trials) showed heterogeneous results: 9 trials were significantly in favor of single vaccination, and 7 were in favor of multiple vaccination, but in most cases, there was no significant difference between the 2 vaccination groups. The pooled serologic protection-rate difference from 52 trials (12341 observations) was again close to 0 (1.7%; 95% confidence interval, -1.3% to 4.8%). CONCLUSIONS: We did not detect any evidence for a decreasing protection with annually repeated influenza vaccination. Annual vaccination should not be discouraged in populations at risk.
BACKGROUND: According to common recommendations, influenza vaccination should be performed annually. It has been suggested that vaccination in previous years reduces vaccine efficacy in the long term. OBJECTIVE: To determine whether the protection of influenza vaccine decreases when vaccination is repeated annually. METHODS: Articles published between 1966 and 1997 were selected from MEDLINE. The end point for field studies was the influenza-related morbidity or mortality during influenza outbreaks (resulting in field protection rates). The end point for serologic studies was exceeding a protective postvaccination hemagglutination-inhibition titer (serologic protection rates). Protection rate differences between groups with single and multiple vaccinations were subjected to meta-analysis. RESULTS: Seven field studies (including 13 trials) supported the hypothesis that protection in multiple-vaccination groups is at least as good as that in single-vaccination groups. Ten trials with 5117 observations could be subjected to meta-analysis. The pooled protection-rate difference was close to 0 (1.1%; 95% confidence interval, -0.2% to 2.4%), thus detecting no difference between single or multiple vaccination. Twelve serologic studies (including 53 trials) showed heterogeneous results: 9 trials were significantly in favor of single vaccination, and 7 were in favor of multiple vaccination, but in most cases, there was no significant difference between the 2 vaccination groups. The pooled serologic protection-rate difference from 52 trials (12341 observations) was again close to 0 (1.7%; 95% confidence interval, -1.3% to 4.8%). CONCLUSIONS: We did not detect any evidence for a decreasing protection with annually repeated influenza vaccination. Annual vaccination should not be discouraged in populations at risk.
Authors: Suzanne E Ohmit; Mark G Thompson; Joshua G Petrie; Swathi N Thaker; Michael L Jackson; Edward A Belongia; Richard K Zimmerman; Manjusha Gaglani; Lois Lamerato; Sarah M Spencer; Lisa Jackson; Jennifer K Meece; Mary Patricia Nowalk; Juhee Song; Marcus Zervos; Po-Yung Cheng; Charles R Rinaldo; Lydia Clipper; David K Shay; Pedro Piedra; Arnold S Monto Journal: Clin Infect Dis Date: 2013-11-13 Impact factor: 9.079
Authors: Suzanne E Ohmit; Joshua G Petrie; Ryan E Malosh; Alicia M Fry; Mark G Thompson; Arnold S Monto Journal: J Infect Dis Date: 2014-11-21 Impact factor: 5.226