TORONTO 91裸聊视频� This season91裸聊视频檚 influenza vaccine is estimated to have been more than 40 per cent effective in preventing illness with the dominant H3N2 viral strain in Canadians who got their shots, a national network of infectious diseases experts says.

The Canadian Sentinel Practitioner Surveillance Network determines vaccine effectiveness by analyzing how many inoculated people tested positive for the flu virus compared to those who were unvaccinated.

91裸聊视频淎 vaccine effectiveness of 40 per cent against the H3N2 virus is decent,91裸聊视频� lead researcher Dr. Danuta Skowronski of the B.C. Centre for Disease Control said Thursday from Vancouver.

91裸聊视频淚t91裸聊视频檚 lower than we would like to see, particularly because H3N2 epidemics tend to be associated with more hospitalizations and deaths. But reducing the risk by 40 per cent is really important, not only at the individual level, but also at the population level when we tally the serious outcomes at the end of the season.91裸聊视频�

Young children, the elderly and people with underlying health conditions like heart disease are vulnerable to complications from flu; H3N2 flu is particularly hard on the elderly.

An effectiveness level of about 40 per cent means the risk of getting sick enough to require medical attention is almost cut in half, and Skowronski said that91裸聊视频檚 important for those at risk of complications.

This season91裸聊视频檚 vaccine, which contained components aimed at preventing illness from two A strains 91裸聊视频� H3N2 and H1N1 91裸聊视频� and a B strain, has been much better at protecting people than the 2014-15 shot, which was mismatched to the H3N2 genetic variant that ended up circulating that season.

The decision on which influenza strains 91裸聊视频� and which particular genetic variations of those strains 91裸聊视频� to target in an upcoming flu season is decided by the World Health Organization (WHO) each February, giving pharmaceutical companies time to produce the vaccine.

But in the intervening months, the viruses can genetically mutate, sometimes leading to such a mismatch as occurred in 2014-15.

Skowronski said vaccine effectiveness levels from Canada and other countries, as well as what genetic mutations might have occurred as the flu bug was passed from person to person over the season, help the WHO decide what strains next season91裸聊视频檚 vaccine should contain.

91裸聊视频淭here91裸聊视频檚 a lot of complexity to the influenza virus. We like to think of it as just a uniform beast, but it91裸聊视频檚 not. It91裸聊视频檚 constantly changing shape, it91裸聊视频檚 constantly evolving.91裸聊视频�

And from what the surveillance network is seeing, next season91裸聊视频檚 vaccine could very well be altered.

91裸聊视频淭here are quite a few emerging variants of H3N2 virus, by province,91裸聊视频� she said, noting that genetic decoding of virus samples in Alberta showed a lot of consistency, but B.C.91裸聊视频檚 cases presented a 91裸聊视频渞ainbow91裸聊视频� on a coloured bar graph. 91裸聊视频淥ntario and Quebec are also showing a smorgasbord of viruses, compared to what Alberta was showing.

91裸聊视频淭his virus is dynamically evolving, real time, during the epidemic. So there91裸聊视频檚 variation 91裸聊视频� that91裸聊视频檚 showing up in this virus as it91裸聊视频檚 trying to evade the immunity in the population.91裸聊视频�

That variation was reflected in vaccine effectiveness in different regions of the country. In Alberta, where influenza activity started earliest and where there was a single dominant H3N2 variant, the shot91裸聊视频檚 effectiveness was estimate at about 60 per cent. In B.C., Ontario and Quebec, where flu activity was delayed and a greater mix of H3N2 genetic variants was detected, the estimate was about 30 per cent.

As of Jan. 28, 12,694 laboratory-confirmed influenza cases had been reported to the Public Health Agency of Canada, according to the most recent figures from its FluWatch report. However, that number represents the 91裸聊视频渢ip of the iceberg91裸聊视频� as most people who get a flu-like illness don91裸聊视频檛 seek medical attention, experts say.

There had also been 2,964 hospitalizations and more than 105 deaths, most of them among adults aged 65 or older.

Skowronski said H3N2 has been responsible for 95 per cent of flu cases this season, but the number of new infections with that viral strain has now begun to wane.

91裸聊视频淚t does look like generally we91裸聊视频檝e turned the corner on this H3N2 wave, we91裸聊视频檙e likely on the down slope of the epidemic curve 91裸聊视频� just,91裸聊视频� she said.

91裸聊视频淎nd now 91裸聊视频� we91裸聊视频檙e starting to pick up some influenza B activity 91裸聊视频� not much, but it91裸聊视频檚 starting 91裸聊视频� and we do often see a tail-end wave of influenza B, so now we91裸聊视频檙e waiting to ride that wave out to the end of the season.91裸聊视频�

The research was published online Thursday in the journal Eurosurveillance (http://eurosurveillance.org/).

91裸聊视频� Sheryl Ubelacker, The Canadian Press