# 5287
We’ve another study – this time from the BMJ – that indicates that the 2009 H1N1 AS03 adjuvanted vaccine – used in Canada and much of Europe - was very effective in preventing the pandemic flu.
Researchers looked at 552 patients consulting their GP’s between Nov 8th and Dec. 5th, 2009 across 4 Canadian provinces and found that the H1N1 virus was detected in 209 of them.
Of those, 2 (1%) had received the pandemic jab at least two weeks earlier, while 58 (17%) patients who had received the shot tested negative.
The researchers found the vaccine to be 93% effective, at least in recipients under the age of 50.
Only 20% of those in the study were over the age of 50, and so further research on the vaccine’s effectiveness in that age group is needed.
First the abstract, then I’ll return with a little more.
- BMJ 2011; 2011; 342:c7297
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, Travis S Hottes, James A Dickinson, Natasha Crowcroft, Trijntje L Kwindt, Patrick Tang, Hugues Charest, Kevin Fonseca, Jonathan B Gubbay, Nathalie Bastien, Yan Li, Martin Petric, clinical virologist
Accepted 22 November 2010
Abstract
Objective To assess the effectiveness of the pandemic influenza A/H1N1 vaccine used in Canada during autumn 2009.
Design Test negative incident case-control study based on sentinel physician surveillance system.
Setting Community based clinics contributing to sentinel networks in British Columbia, Alberta, Ontario, and Quebec, Canada.
Participants 552 patients who presented to a sentinel site within seven days of onset of influenza-like illness during the primary analysis period between 8 November and 5 December 2009; participants were mostly (>80%) children and adults under 50 years old.
Interventions Monovalent AS03 adjuvanted pandemic influenza A/H1N1 vaccine as the predominant formulation (>95%) distributed in Canada.
Main outcome measures Vaccine effectiveness calculated as 1−(odds ratio for influenza in vaccinated (received pandemic H1N1 vaccine at least two weeks before onset of influenza-like illness) versus unvaccinated participants), with adjustment for age, comorbidity, province, timeliness of specimen collection, and week of illness onset. Sensitivity analyses explored the influence of varying analysis periods between 1 November and 31 December, receipt of trivalent seasonal influenza vaccine, and restriction to participants without comorbidity.
Results 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% (95% confidence interval 69% to 98%). High estimates of vaccine protection—generally at least 90%—were maintained across most sensitivity analyses.
Conclusions 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.
While limited by its relatively small size, this study adds to the weight of evidence showing that the 2009 pandemic vaccine was very effective in preventing the flu.
Last month we saw two studies released showing that the unadjuvanted vaccine provided an adjusted vaccine effectiveness for adults under 65 of about 72%.
Eurosurveillance: Another Pandemic Vaccine Effectiveness Study
In May of 2010 we saw a comparison study (see BMJ: Immunogenicity Of Adjuvanted vs. Unadjuvanted H1N1 Vaccines) between GSK’s Pandemrix, containing the adjuvant AS03, verses Baxter’s unadjuvanted Celvapan in British children.
Although the adjuvanted Pandemrix vaccine was associated with a higher rate of (usually mild) side effects (fever, injection site soreness), it produced a superior immune response.
While there remain some open questions regarding the Pandemrix vaccine and reports of narcolepsy in adolescents and children in some Scandinavian countries, except for a handful of suspected adverse events under investigation, the safety profile of the adjuvanted vaccine has been excellent.
Lancet: Immunogenicity and safety Of Adjuvanted Flu Vaccines
While admittedly not 100% perfect, the adjuvanted and unadjuvanted 2009 H1N1 pandemic vaccines have proven themselves to have been very safe, and very effective.
Given the short time in which scientists, manufacturers, and public health agencies had to identify, isolate, grow, test, and distribute a pandemic vaccine - despite some bumps along the way – it is hard not to view this emergency vaccination program as a remarkable success.
