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



This observer-blind, randomized, placebo-controlled study enrolled adults aged 18-64years 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 14days after vaccination until 30 November of each study year were tested for influenza by real-time reverse transcription polymerase chain reaction.



Over a study period of 2years, 15,044 participants were enrolled (mean age±standard deviation: 35.5±14.7years; 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).



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.
James Cook University, Cairns Hospital Clinical School, Cairns, Queensland 4870, Australia. Electronic address: john.mcbride@jcu.edu.au.
William J H
WJH
Mcbride
Academic Unit of Internal Medicine, Canberra Hospital, Woden, Australian Capital Territory 2606, Australia; ANU College of Medicine, Biology and Environment, Australian National University, Canberra, Australian Capital Territory 0200, Australia. Electronic address: walter.abhayaratna@act.gov.au.
Walter P
WP
Abhayaratna
World Health Organization Collaborating Centre for Reference and Research on Influenza, North Melbourne, Victoria 3051, Australia. Electronic address: Ian.Barr@influenzacentre.org.
Ian
I
Barr
National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, The University of Sydney and The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia. Electronic address: Robert.booy@health.nsw.gov.au.
Robert
R
Booy
Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory 0810, Australia. Electronic address: jonathan.carapetis@telethonkids.org.au.
Jonathan
J
Carapetis
Southern Clinical Trials Ltd, Christchurch 8013, New Zealand. Electronic address: Simon.Carson@cshc.co.nz.
Simon
S
Carson
Trialworks Clinical Research Pty Ltd and Discipline of General Practice, School of Medicine, University of Queensland, Brisbane, Queensland 4067, Australia. Electronic address: freddelooze@austrials.com.au.
Ferdinandus
F
De Looze
Auckland Clinical Studies, Auckland 1072, New Zealand. Electronic address: rodbep@gmail.com.
Rod
R
Ellis-Pegler
National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, The University of Sydney and The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia. Electronic address: LeonH@chw.edu.au.
Leon
L
Heron
Redcliffe Hospital, Redcliffe, Queensland 4020, Australia. Electronic address: jeffkarrasch@gmail.com.
Jeff
J
Karrasch
Vaccinology and Immunology Research Trials Unit (VIRTU), Women's and Children's Hospital, Robinson Research Institute and School of Medicine, University of Adelaide, Adelaide, South Australia 5006, Australia. Electronic address: helen.marshall@adelaide.edu.au.
Helen
H
Marshall
Vaccine and Immunization Research Group, Melbourne School of Population and Global Health, University of Melbourne, and Murdoch Children's Research Institute, Parkville, Victoria 3052, Australia. Electronic address: j.mcvernon@unimelb.edu.au.
Jodie
J
Mcvernon
Vaccine and Immunization Research Group, Melbourne School of Population and Global Health, University of Melbourne, and Murdoch Children's Research Institute, Parkville, Victoria 3052, Australia. Electronic address: t.nolan@unimelb.edu.au.
Terry
T
Nolan
South Eastern Sydney and Illawarra Area Health Service and University of New South Wales, Sydney, New South Wales 2052, Australia. Electronic address: w.rawlinson@unsw.edu.au.
William
W
Rawlinson
Dunedin School of Medicine, University of Otago, Dunedin 9054, New Zealand. Electronic address: jim.reid@otago.ac.nz.
Jim
J
Reid
University of Western Australia, School of Paediatrics and Child Health, Princess Margaret Hospital for Children, Perth, Western Australia 6872, Australia.
Peter
P
Richmond
Discipline of Pharmacology, School of Medical Sciences, University of Adelaide, Adelaide, South Australia 5001, Australia. Electronic address: ssshakib@gmail.com.
Sepehr
S
Shakib
Clinical Research and Development, CSL Limited, Parkville, Victoria 3052, Australia. Electronic address: Russell.Basser@seqirus.com.
Russell L
RL
Basser
Clinical Research and Development, CSL Limited, Parkville, Victoria 3052, Australia. Electronic address: Gunter@HartelConsulting.com.
Gunter F
GF
Hartel
Clinical Research and Development, CSL Limited, Parkville, Victoria 3052, Australia. Electronic address: michael_h.lai@novartis.com.
Michael H
MH
Lai
Clinical Research and Development, CSL Limited, Parkville, Victoria 3052, Australia. Electronic address: Steve.Rockman@seqirus.com.
Steven
S
Rockman
Clinical Research and Development, CSL Limited, Parkville, Victoria 3052, Australia. Electronic address: Michael.greenberg@sanofipasteur.com.
Michael E
ME
Greenberg
D000328:Adult; D001315:Australia; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D055815:Young Adult
D007252:Influenza Vaccines
Cross-protection; H1N1 subtype; Influenza A virus; Influenza vaccine efficacy; Seasonal influenza; Seasonal trivalent inactivated influenza vaccine