The “triple epidemic” could have been worse. The flu vaccine has been shown to be effective this year, US data released on Thursday show. They confirm Canadian data from the beginning of the month.
“Usually, there is a lower effectiveness of the flu vaccine against the H3N2 strain which dominates this year”, explains Gaston De Serres, epidemiologist at the National Institute of Public Health of Quebec (INSPQ). “This year, the numbers are good. »
The effectiveness unveiled Thursday by the Centers for Disease Control and Prevention (CDC) of the US government ranged from 54% to 71% depending on age group. This compares to 48% to 59% for Canadian data published in early February in the journal Eurosurveillancein a study whose Dr De Serres is co-author.
These efficacy data are different from those for COVID-19 vaccines, which focus on protection against serious diseases. “What we measure with the effectiveness of flu shots is protection against a flu bad enough to go see the doctor,” says Dr.r From Serres.
Better performance against H1N1
Since 2005, the effectiveness of the Canadian influenza vaccine against the H3N2 strain has never exceeded 57%, and has sometimes been as low as 14%, according to data from the Canadian Primary Care Sentinel Surveillance Network. Against the H1N1 strain, the performance is better: the lowest performance was 43% and the efficiency exceeded 90% on two occasions, notably during the 2009 pandemic.
“In 2009, we used an adjuvant, the vaccine worked very well, but we administered it too late in the pandemic,” says Dr.r From Serres. Why didn’t you continue to use this adjuvant? “There were narcolepsy issues in rare cases,” says Dr.r From Serres.
The H5N1 threat
In January, in Eurosurveillance, another threat has emerged: the H5N1 flu strain, which has been responsible for the slaughter of half a million poultry in Quebec over the past year. “We have seen transmission in mink in Spain, explains the Dr From Serres. The mink is a cousin of the ferret, which is very similar to humans for influenza infections. So that concerns us. » Does the mRNA vaccine revolution that helped contain COVID-19, thanks to the companies BioNTech and Moderna, constitute a shield against an H5N1 pandemic and make it possible to avoid confinements and other cover-ups? lights? “I would say those companies must definitely be working on H5N1,” says Dr.r From Serres. That said, COVID-19 is much more contagious than the flu, so I’m not sure we’re going to go back to lockdown anyway. »
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- Effectiveness of the influenza vaccine against the H3N2 strain in 2021-2022 in Canada
SOURCE: INSPQ