The flu vaccine this season seems to be very effective, reducing the risk of infection with the dominant circulating influenza strain by more than 70% – far better than what is seen in last year's shots, Canadian researchers say.
Their mid-season analysis published on Thursday in Euro Surveillance magazine shows that this year's influenza vaccine is 72% effective in preventing H1N1 respiratory infection in all age groups.
The result is "good news," said lead researcher Dr Danuta Skorowski of the Center for Disease Control, bearing in mind that last year's efficacy was less than 20 percent, mainly due to a discrepancy between the vaccine and the H3N2 strain . which predominate during the season 2017-18.
Another reason is that flu vaccine performs better during H1N1-dominated seasons, she said, noting that Australia reported comparative performance ratings using the same wording during the last flu season.
Efficiency of about 70% means that inoculation would prevent seven of the ten cases of flu in unvaccinated people if they chose to shoot, explained Skouronski, a BCC flu influenza expert.
"So this is really a significant risk reduction, especially for people with hidden illnesses who face a greater threat of serious complications if they are infected with flu," she said from Vancouver. "They could reduce this risk by 70 percent."
By age group, the vaccine was found to be 91% effective in children aged one to eight; 71% for children aged 9 to 19; An average of 68% for adults aged 20 to 64; and 65% of those aged 65 and over.
Because H1N1 dominates, young children are particularly heavily affected by influenza this year – probably because they had little or no previous exposure to this virus strain and therefore did not develop natural immunity. The last three H1N1 epidemics occurred in 2015-16, 2013-14 and 2009 when some of today's children would not be born.
As of January 12, more than 600 children aged 16 and under were hospitalized, with 93 of them in intensive care and at least seven – all under 10 – dying of complications from influenza, say the Public Health Agency of Canada (PHAC). The death of a three-year-old girl from Quebec last week would not be caught in this report.
Scourronski said children are disproportionately affected by influenza this year, with children under the age of 9 accounting for 28% of the 661 cases analyzed for vaccine efficacy, although children are only about 10% of the country's population.
"That's why I think this year we see the younger people represented in the number of H1N1 hospitalizations," she said. "Not that the virus is more virulent." We have higher levels of attack in younger children.
"When you have more infected, higher levels of attack, and the same percentage is serious, the absolute result of serious results will be higher."
On its FluWatch weekly, PHAC said there were 20,494 laboratory confirmed cases of influenza reported by the provinces and territories on January 12, most of which were caused by H1N1 and most affected those under 65.
More than 1,500 are the result of hospitalization, including 227 admissions for intensive care and 47 deaths.
PHAC collects data only for laboratory-confirmed cases of people who have been tested after seeking medical attention. The actual number of Canadians who have infected with flu without seeing a healthcare provider would be many times higher.
The analysis of vaccine efficacy was conducted by researchers with the Sentinel Canadian Sentinel Surveillance Network, based in BCCDC. The network includes hundreds of primary care practitioners in the UK, Alberta, Ontario and Quebec, who collect positive results from flu tests and vaccination status of infected patients on an outpatient basis. Patients treated in a hospital are not included in the data.
Scorronski said there are many regional differences in the time and intensity of the flu epidemic across the country. Alberta and BK, for example, began to see cases at the beginning of the season, while the regions in eastern Canada were later affected and may have not reached their peak.
"We went through the summit here and we are downhill," she told the BC. "But even when the epidemic curve falls, it will work for a few more weeks.
So it's not too late for people who have not been vaccinated to get a shot, especially in the regions of the country who are still seeing rising incidents, "Skoronski said.
"That's why it was important for us to get this (vaccine effectiveness) assessment because it offers significant protection that can still be important in areas where there is increased activity.
"And do not forget that influenza B has not shown much of this year and usually appears later in the season."
Last season, only 38% of Canadian adults received the flu vaccine, with vaccine intake varies with age and risk factors for complications, a PHAC spokeswoman said.
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