Elsevier

Vaccine

Volume 34, Issue 41, 22 September 2016, Pages 4991-4997
Vaccine

Efficacy of a trivalent influenza vaccine against seasonal strains and against 2009 pandemic H1N1: A randomized, placebo-controlled trial

https://doi.org/10.1016/j.vaccine.2016.08.038Get rights and content
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open access

Highlights

  • Two seasonal IIV3s showed efficacy against vaccine-matched strains in adults.

  • The 2009 seasonal IIV3 showed efficacy against the 2009 pandemic H1N1 strain.

  • Most solicited adverse events were of mild/moderate intensity and limited duration.

Abstract

Background

Before pandemic H1N1 vaccines were available, the potential benefit of existing seasonal trivalent inactivated influenza vaccines (IIV3s) against influenza due to the 2009 pandemic H1N1 influenza strain was investigated, with conflicting results. This study assessed the efficacy of seasonal IIV3s against influenza due to 2008 and 2009 seasonal influenza strains and against the 2009 pandemic H1N1 strain.

Methods

This observer-blind, randomized, placebo-controlled study enrolled adults aged 18–64 years during 2008 and 2009 in Australia and New Zealand. Participants were randomized 2:1 to receive IIV3 or placebo. The primary objective was to demonstrate the efficacy of IIV3 against laboratory-confirmed influenza. Participants reporting an influenza-like illness during the period from 14 days after vaccination until 30 November of each study year were tested for influenza by real-time reverse transcription polymerase chain reaction.

Results

Over a study period of 2 years, 15,044 participants were enrolled (mean age ± standard deviation: 35.5 ± 14.7 years; 54.4% female). Vaccine efficacy of the 2008 and 2009 IIV3s against influenza due to any strain was 42% (95% confidence interval [CI]: 30%, 52%), whereas vaccine efficacy against influenza due to the vaccine-matched strains was 60% (95% CI: 44%, 72%). Vaccine efficacy of the 2009 IIV3 against influenza due to the 2009 pandemic H1N1 strain was 38% (95% CI: 19%, 53%). No vaccine-related deaths or serious adverse events were reported. Solicited local and systemic adverse events were more frequent in IIV3 recipients than placebo recipients (local: IIV3 74.6% vs placebo 20.4%, p < 0.001; systemic: IIV3 46.6% vs placebo 39.1%, p < 0.001).

Conclusions

The 2008 and 2009 IIV3s were efficacious against influenza due to seasonal influenza strains and the 2009 IIV3 demonstrated moderate efficacy against influenza due to the 2009 pandemic H1N1 strain.

Funded by CSL Limited, ClinicalTrials.gov identifier NCT00562484

Keywords

Cross-protection
Influenza A virus
H1N1 subtype
Influenza vaccine efficacy
Seasonal influenza
Seasonal trivalent inactivated influenza vaccine

Cited by (0)

1

Present address: Modelling and Simulation Unit, Melbourne School of Population and Global Health, The University of Melbourne, Victoria 3010, Australia and Murdoch Childrens Research Institute, Parkville, Victoria 3052, Australia.

2

Present address: Hartel Consulting, Brisbane, Queensland 4170, Australia.

3

Present address: Novartis Pharma AG, Retina Development Franchise, Novartis Campus, 4056 Basel, Switzerland.

4

Present address: Sanofi Pasteur, San Francisco, CA 94107, USA.