Ineffective flu vaccine? | HuffPost Life

Each year in November, the Quebec Ministry of Health and Social Services launches its vaccination campaign against seasonal flu. Although the effectiveness of the vaccine was disappointing a few years ago, vaccination remains an important way to reduce complications and hospitalizations related to influenza, especially among people at risk. Why the effectiveness of the flu vaccine In 2014 – 2015, the effectiveness of the flu shot had been particularly low. Many websites took the opportunity to confuse the inefficiency of this vaccine that year with the inefficiency of vaccines in general. But we must remember that the flu is a special case. Three characteristics of the influenza virus explain that it is difficult to develop a single vaccine that would have the same effectiveness, year after year.1) It is not just “a” flu According to the World Health Organization ( WHO), there are three types of influenza viruses, called A, B and (less common) C. Type A itself is divided into subtypes, depending on the protein on the surface of the virus. These proteins play a role in the spread of the virus and are designated by the letters H (haemagglutinin) and N (neuraminidase) .But from one year to another, influenza strains in circulation are not necessarily the same and they can even coexist, forcing to develop a new vaccine every year. For example, in 2015 – 2016, strain A (H1N1) caused 54% of cases; virus B was responsible for 37% of cases. On the other hand, in 2018 – 2019, strain A (H1N1) was responsible for 89 % of cases, strain A (H3N2) 6% and strain B only 1% .2) Influenza virus has a high rate of mutation Influenza virus also has the unfortunate habit of modifying itself, of undergoing mutations, which makes it harder to detect by the immune system.It must be remembered that if our immune system is able to effectively combat an attacker -as a virus- it’s because he has already met. In other words, he recognizes it. This is the basic principle of any vaccination, which involves injecting a harmless version of the virus, so that the immune system recognizes it later. However, the mutations of the influenza virus modify its surface proteins. These are then more difficult to recognize, or not recognized at all, by the immune system.Pornpak Khunatorn via Getty Images3) Strains in circulation are difficult to predict Finally, it is difficult to predict what will be the strain of influenza that will be in during the next season. Since 1973, WHO has issued formal recommendations on this subject. “Sentinel surveillance centers around the world are sequencing the genome of circulating viruses,” says Martin Richter of the CHUS Research Center, who is interested in the immunology and pharmacology of respiratory viral infections. “According to the results from one part of the world, WHO is doing statistics and predicting which strains should spread in North America, which makes it possible to develop vaccines. In Canada, the Influenza Task Force then develops its own recommendations for submission to the National Advisory Committee on Immunization. “But scientists can be wrong in choosing the strain,” says Dr. Karl Weiss. , a microbiologist and infectious disease physician at the Jewish General Hospital in Montreal. “A lot of mistakes can happen. This explains the inefficiency observed in 2014 – 2015. The strain used to make the vaccine differed genetically from that in circulation.What is the average effectiveness of the flu vaccine? According to the Quebec government website, the flu vaccine prevents the disease in 40 Has people in good health, provided that the strains contained therein correspond to those in circulation. For the season 2018 – 2019 in particular, Canadian scientists have assessed that the vaccine has provided 72% against the A (H1N1) virus, then circulating. However, research suggests that it may be less effective in the elderly. “Efficiency also varies from person to person,” explains Richter. In addition, to have a good efficiency, we aim for a vaccination rate in the population of at least 80%. If too few people are vaccinated, the community will not be very well protected. In the Quebec population, although vaccination coverage is high among people with chronic illness or in the elderly, it does not reach the target proportion, except for CHSLD residents. Who should be vaccinated against influenza? According to a report published in 2018 by the Quebec Committee on Immunization (CIQ), on average, 6194 Quebecers have been hospitalized annually because of flu between – 2012 and 2015 – 2016 . Of these, 80% already had a chronic illness. Moreover, more than half of the deaths associated with influenza occur among CHSLD residents. Although healthy people are, for the most part, rarely hospitalized for influenza, the CIQ still focused on the relevance of including healthy people in the influenza immunization program. After conducting an economic analysis, the CIQ came to the conclusion that it was not desirable to extend influenza vaccination to the general population. He even suggested removing from the list of at-risk groups children from 6 to 23 months, as well as adults from 60 to 74 years health. By removing them, it would become easier to reach the target of 80% of immunization coverage in groups actually at risk, such as people with chronic illness and those older than 75 years. “Even if it’s not a very good vaccine, reducing the risk of going to the hospital, we avoid serious consequences,” says Dr. Weiss. Finally, we must remember that the annual vaccine against influenza works only against the flu virus. The problem here is that the Centers for Disease Control and Prevention (CDC) in the United States, report that several other viruses can cause similar symptoms that can be confused with the flu, even by a doctor. For example, the effectiveness of the vaccine is higher if it is calculated based solely on laboratory-confirmed influenza cases, rather than on all cases diagnosed by a physician, according to the National Advisory Committee of the Canadian Institutes of Health. immunization.- This text is an update of an article originally published in November 2016
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