Protection Against Influenza after Annually Repeated Vaccination

A systematic review 1 including 7 studies (10 trials) with a total of 5117 subjects in the field studies and 52 trials with a total of 12,341 subjects in serologic studies was abstracted in DARE. The study question was whether the protection rate decreases if vaccinations are repeated annually. The pooled protection-rate difference in field studies was close to 0, thus detecting no difference between single and multiple vaccinations. In the serologic studies, 9 trials were significantly in favour of single vaccination, and 7 trials were in favour of multiple vaccination.

Comment: The quality of evidence is downgraded by indirectness of evidence (mostly surrogate (serological) outcomes).

The following decision support rules contain links to this evidence summary:

• Influenza vaccination for the elderly http://www.ebmeds.org/ebmeds/ebmeds_home.asp?mode=scripts&submode=view&id=scr00478&country=UK
• Influenza vaccination for risk groups http://www.ebmeds.org/ebmeds/ebmeds_home.asp?mode=scripts&submode=view&id=scr00493&country=UK

References

• Beyer WE, de Bruijn IA, Palache AM, Westendorp RG, Osterhaus AD. Protection against influenza after annually repeated vaccination: a meta-analysis of serologic and field studies. Arch Intern Med 1999 Jan 25;159(2):182-8. [PubMed] [DARE]