For the first time, Canada is providing flu vaccines providing protection against four strains of the virus. Previous versions had only three strains. Our 2015 flu shot protects against:
- A/California/7/2009 (H1N1)pdm09-like virus
- A/Switzerland/9715293/2013 (H3N2)-like virus
- B/Phuket/3073/2013-like virus
- B strain – a B/Brisbane/60/2008-like virus
By most accounts the flu vaccine for 2015/2016 is not as efficacious as hoped, but getting it is still better than not getting it. Early data suggests that the vaccine effectiveness (VE) will be around 40-50%. Expressed as a percentage, VE represents the reduction in the risk that a person will need to visit a hospital or doctor’s office because of the flu. The CDC (Centers for Disease Control) is reporting an overall VE of 23% for North America. Even if the VE turns out to be on the low side it still means that 23% fewer of us will need medical care because of the flu and that’s nothing to sneeze at. According to Health Canada, seasonal flu results in approximately 12,200 hospitalizations and 3,500 deaths in our country every year. A 23% reduction means over 800 lives saved and thousands more avoiding the emergency room.
For some reason a January 2015 news item with misleading headlines about the low VE of the 2014 vaccine has been circulating again, perhaps in an effort to discredit the 2015 shot. One headline implied that the 2014 vaccine made it “more likely” that you would get the flu. What they should have said was that it was slightly less effective than the previous year’s formulation, not less effective than going vaccine-free. One of the most reported studies found that the VE for one of the 2014 flu vaccines offered in Canada was 69% if you had not had the vaccine in 2013 but only 65% if you had been vaccinated for both years. In other words, it was slightly more likely that you would get the flu in 2014 if you had vaccinations two years in a row, but the risk reduction was still 65% over no vaccine at all. So either way, you were much better off getting the shot in 2014.
Official reports of the 2014/2015 vaccine’s VE varied widely across North America. Since the strains to be included in the vaccine are chosen months ahead of the flu season, sometimes there is a mismatch between the vaccine strains and the ones that end up circulating in Canada, varying from region to region. Occasionally the strains mutate enough that the effectiveness of the vaccine is lessened. Health Canada also attributes some of the overall VE drop to a problem with stability of the A/California H1N1 vaccine strain when exposed to temperature fluctuations. This happened mostly in California where the vaccines were subjected to heat that rendered them less effective. The National Advisory Committee on Immunizations concluded that this is unlikely to be a problem in Canada because we have requirements for the maintenance of proper temperatures at all times. Monitoring devices or carrier logs are required to provide evidence that proper conditions were maintained.
Along with handwashing and plumbing, vaccines are among the safest, most important medical advances of all time and they are offered free or almost free to all Canadians. We should take full advantage of it.
Blythe Nilson, CFIC Science Chair
- Health Canada: http://www.phac-aspc.gc.ca/naci-ccni/flu-2015-grippe-eng.php#i1
- CDC 2015-2016 Flu Vaccines: http://www.cdc.gov/flu/about/season/flu-season-2015-2016.htm
- CDC Vaccine FAQ: http://www.cdc.gov/flu/about/qa/vaccineeffect.htm
- U. Manitoba Report: http://www.cidrap.umn.edu/news-perspective/2014/11/study-adds-more-data-effects-consecutive-year-flu-shots