Canadian Department of Health scientists discovered that if people in British Columbia received last year's seasonal flu shot, they were twice as likely to contract swine flu this year. My guess is that the researchers were trying to learn whether last year's flu vaccine conferred any protection against swine flu--and what they discovered instead was that it increased susceptibility.
Other vaccines (experimental, or no longer licensed) have occasionally promoted rather than protected against the disease one was vaccinated for, or induced another disease. An experimental HIV vaccine increased cases of HIV recently. According to former CDC director Jeffrey Koplan, the1960s KMV measles vaccine caused a new illness in recipients who were later exposed to measles. The new illness, termed atypical measles, was much more serious and prolonged than ordinary measles.
In any event, the British Columbia information was shared, and confirmed by researchers in other Canadian provinces using new datasets. The data were reviewed at multiple levels. Finally, the Canadians halted their seasonal flu vaccine program for those at risk of swine flu, considering it the larger threat and seasonal flu vaccine avoidance to be prudent. Since persons over 65 are at low risk of a serious swine flu outcome, and traditionally more at risk from seasonal flu than a younger population, their seasonal flu shots were continued.
Policymakers at WHO and the US found this difficult to deal with. Canada was adapting the policy to the science. Despite sharing its data, which an international panel determined had "merit," Canada alone rebuilt its flu response.
Mexico has now rushed out conflicting data suggesting the seasonal flu vaccine might instead be protective against swine flu deaths. No word on how well or if the Mexican data were reviewed. Maggie Fox reported this story; she earlier reported misinformation on the 1976 vaccine link to GBS.
(Data similar to that from Mexico suggested seasonal flu shots caused winter deaths in the elderly to fall by 50%--until it was noticed flu only caused about 5% of elderly deaths--and the spurious impression of a 50% reduction in deaths from the vaccine was because elders who were vaccinated were in better health than those who were not.)
Here is an excerpt from the WSJ story:
Twelve of Canada's 13 provinces and territories are delaying the rollout of seasonal-flu shots for the bulk of their populations until after their H1N1 inoculations are complete -- likely at the end of this year.
The study "wasn't something we felt we could ignore," said Perry Kendall, provincial health officer for British Columbia, which like most provinces is limiting seasonal-flu shots to people ages 65 and older until after it has finished its H1N1 vaccinations. "Why would you want to run the risk of doubling peoples' risk of getting H1N1?" said Dr. Kendall, who noted that he has seen the data and talked to the study's authors.
The study began after researchers in British Columbia this summer found a possible link between contracting H1N1 and receiving flu shots the previous season, for some people in the province.
The researchers shared the information with colleagues in the other provinces, some of whom in turn found their own links, said Dr. Kendall. Those results were collated into one study covering about 2,000 confirmed cases of H1N1 in places such as British Columbia, Ontario and Quebec. It found that people who got flu shots last year were about twice as likely to contract swine flu as those who weren't vaccinated, according to sources who have seen the study's data.
The Public Health Agency of Canada commissioned an international panel of experts to take a look at the study's methodology; that panel last week said it found no methodological errors and that the study has "merit," an agency spokeswoman said...