Was the monovalent H1N1 vaccine effective?

January 01, 0001

Was the monovalent H1N1 vaccine effective?

The H1N1 pandemic created much consternation in 2009, as health care systems struggled to deal with the novel influenza virus. These Canadian researchers tested the efficacy of the pandemic influenza A/H1N1 vaccine via a test negative incident case-control study based on sentinel physician surveillance system. The study looked at Canadian patients who presented to a sentinel site within one week influenza-like illness onset (n=552) during the the final two months of 2009. The participants were primarily children and young adults. Results were adjusted for age, comorbidity, timeliness of specimen collection, and week of illness onset.

The researchers found: "During the primary analysis period, pandemic H1N1 was detected by reverse transcription polymerase chain reaction in 209/552 (38%) participants. Rates were highest in children and young adults (40%) and lowest in people aged 65 or over (9%). Among the 209 cases, 35 (17%) reported comorbidity compared with 80/343 (23%) controls. Two (1%) cases had received pandemic H1N1 vaccine at least two weeks before the onset of illness, compared with 58/343 (17%) controls, all single dose. Adjusted vaccine effectiveness overall was 93%. High estimates of vaccine protection—generally at least 90%—were maintained across most sensitivity analyses."

The researchers concluded: "Although limited by a small number of vaccine failures, this study suggests that the monovalent AS03 adjuvanted vaccine used in Canada during autumn 2009 was highly effective in preventing medically attended, laboratory confirmed pandemic H1N1 illness, with reference in particular to a single dose in children and young adults."

This examination finds the monovalent influenza A/H1N1 vaccine was clinically effective in preventing influenza.

For the full abstract, click here.

BMJ 342:c7297, 3 February 2011
© 2011 BMJ Publishing Group Ltd.
Effectiveness of AS03 adjuvanted pandemic H1N1 vaccine: case- control evaluation based on sentinel surveillance system in Canada, autumn 2009. Danuta M Skowronski, Naveed Z Janjua, Gaston De Serres, et al. Correspondence to D M Skowronski: danuta.skowronski@bccdc.ca

Category: B. Blood/Immune Mechanisms, R. Respiratory. Keywords: influenza, influenza A, H1N1, vaccination, monovalent, case-control, journal watch.
Synopsis edited by Dr Paul Schaefer, Toledo, Ohio. Posted on Global Family Doctor 22 February 2011

Pearls are an independent product of the Cochrane primary care group and are meant for educational use and not to guide clinical care.