TORONTO 香蕉视频直播� This season香蕉视频直播檚 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.

香蕉视频直播淎 vaccine effectiveness of 40 per cent against the H3N2 virus is decent,香蕉视频直播� lead researcher Dr. Danuta Skowronski of the B.C. Centre for Disease Control said Thursday from Vancouver.

香蕉视频直播淚t香蕉视频直播檚 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.香蕉视频直播�

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 that香蕉视频直播檚 important for those at risk of complications.

This season香蕉视频直播檚 vaccine, which contained components aimed at preventing illness from two A strains 香蕉视频直播� H3N2 and H1N1 香蕉视频直播� 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 香蕉视频直播� and which particular genetic variations of those strains 香蕉视频直播� 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 season香蕉视频直播檚 vaccine should contain.

香蕉视频直播淭here香蕉视频直播檚 a lot of complexity to the influenza virus. We like to think of it as just a uniform beast, but it香蕉视频直播檚 not. It香蕉视频直播檚 constantly changing shape, it香蕉视频直播檚 constantly evolving.香蕉视频直播�

And from what the surveillance network is seeing, next season香蕉视频直播檚 vaccine could very well be altered.

香蕉视频直播淭here are quite a few emerging variants of H3N2 virus, by province,香蕉视频直播� she said, noting that genetic decoding of virus samples in Alberta showed a lot of consistency, but B.C.香蕉视频直播檚 cases presented a 香蕉视频直播渞ainbow香蕉视频直播� on a coloured bar graph. 香蕉视频直播淥ntario and Quebec are also showing a smorgasbord of viruses, compared to what Alberta was showing.

香蕉视频直播淭his virus is dynamically evolving, real time, during the epidemic. So there香蕉视频直播檚 variation 香蕉视频直播� that香蕉视频直播檚 showing up in this virus as it香蕉视频直播檚 trying to evade the immunity in the population.香蕉视频直播�

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 shot香蕉视频直播檚 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 香蕉视频直播渢ip of the iceberg香蕉视频直播� as most people who get a flu-like illness don香蕉视频直播檛 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.

香蕉视频直播淚t does look like generally we香蕉视频直播檝e turned the corner on this H3N2 wave, we香蕉视频直播檙e likely on the down slope of the epidemic curve 香蕉视频直播� just,香蕉视频直播� she said.

香蕉视频直播淎nd now 香蕉视频直播� we香蕉视频直播檙e starting to pick up some influenza B activity 香蕉视频直播� not much, but it香蕉视频直播檚 starting 香蕉视频直播� and we do often see a tail-end wave of influenza B, so now we香蕉视频直播檙e waiting to ride that wave out to the end of the season.香蕉视频直播�

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

香蕉视频直播� Sheryl Ubelacker, The Canadian Press