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Last year's extremely bad flu season is behind us, and the number is imminent: 80,000 people have died as a result of the flu or its complications, and 900,000 people have been in hospital. Last year, much of the misery came from the H3N2 virus, a particularly serious influenza strain that caused more severe symptoms than other strains and was poorly matched to last season's vaccine. Add to that a growing population of people aged 65 and over, who are most likely to develop complications related to the flu, and this has been a record year.
So what should we expect this year? The experts are asking the same question. "The flu is predictably unpredictable," said Alicia Budd, an epidemiologist with the Division of Influenza Centers for Disease Prevention and Control. "We really have no way of predicting exactly what we are going to see." And this makes it difficult to manufacture the vaccine, which is produced months in advance. Influenza viruses mutate and evolve very quickly, so it's hard to predict what will happen.
Nevertheless, there is a reason for cautious hope. The southern hemisphere has had an extremely mild flu season this year, said William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center. The predominant virus in the southern hemisphere was the H1N1 virus, and it is this strain that has appeared up to now in the influenza season among the first influenza viruses in the United States. "Combine these two elements and we can hope for a lenient season, but I'm still nervous about saying that," Schaffner said. "The flu is unstable." We will not know how this year's season will go before the end.
Also fickle: the flu vaccine. But it's still worth it. An influenza vaccine can reduce your risk of influenza infection and reduce the risk of spreading the virus. While it's true that flu vaccine is not as effective as childhood vaccines, such as the measles, mumps and rubella vaccine, that's no reason to ignore it, said Michael. Osterholm, Director of the Center for Infectious Disease Research and Related Policies. University of Minnesota. Last year, the influenza vaccine was effective at about 40% (meaning that a person vaccinated was about 40% less likely to get enough of the flu to see a doctor). And that's about the average of the last 14 seasons of the flu. It may sound unimpressive, but "it's way better than zero," said Osterholm. And studies suggest that even if it does not prevent the flu in any case, it could still reduce the severity of the symptoms, he said.
The ability of the vaccine to prevent influenza depends in part on its adequacy to circulating strains. Every year, experts from around the world gather to decide on the vaccine's content for the season. "Decisions about vaccines in people's arms have now been made in February of this year," said Budd. This is because it takes time to produce and distribute the vaccine in time for the influenza season. This year's vaccine was adjusted in part to address a manufacturing problem that appeared to have reduced the effectiveness of last year's vaccine.
Most influenza vaccines are made from growing influenza viruses in eggs and this process can lead to slight mutations in viruses. "What you started is not what you finished, and that could reduce the effectiveness of a vaccine," said Edward Belongia, an epidemiologist at the Marshfield Clinic Research Institute in Wisconsin. The problem seems most important for H3N2 viruses, which tend to evolve faster than other strains. This year's vaccine contains four strains and its H3N2 strain seems less prone to these "egg-friendly" changes than last year. We therefore hope that it will offer more protection against these types.
Another important but misunderstood problem is that influenza vaccines seem to be losing their effectiveness relatively quickly. A study published last month in the journal Clinical Infectious Diseases examined data from seven influenza seasons and showed that the effectiveness of influenza vaccine decreased by 16% every four weeks after the administration of the vaccine. So, if you get the vaccine in October, you will not be as protected in December as in November. The study is just one of many conclusions that the more time has passed since the flu shot, the less protection it offers, said Marc Lipsitch, Professor of Epidemiology at Harvard TH Chan School. of Public Health who wrote an editorial that accompanied the newspaper. But these studies all share methodological flaws, he said: Calculating the effectiveness of an influenza vaccine is a difficult challenge. "As a scientist, I would say we do not know it yet."
When I spoke to him on Wednesday, Lipsitch said he had a doctor's appointment that day, but did not plan to get the flu shot. "I will probably wait a month or two," he said. "I consider the evidence, however imperfect, convincing enough that waiting is almost certainly not a bad thing." That is, unless not talking about it means that you have never resorted to the vaccine, he said. In other words, if you're a procrastinator like me, it's probably best to get it when it's in front of you to assume that you'll get there later.
But places that offer vaccines could help by adjusting their timing. (My local pharmacy began offering it in August.) To this end, the CDC's Advisory Committee on Immunization Practices has recently modified its recommendations regarding timing so as not to mislead it. 39, get it as soon as it will be available, but get it by the end of October. Said Osterholm. It may seem easy to wait until the vaccine season begins to be felt, but it takes about two weeks to gain immunity. Therefore, waiting too long could easily turn against us. Making the right timing is "a bit like riding the big waves in Maui," Osterholm said. "Too far ahead, you're dead." Osterholm said the last 10 seasons of influenza, with the exception of the 2009 pandemic, all started between the middle and the end of December, making the October a sure enough bet.
In the end, what we really need is a better vaccine. The latest iterations are "not the vaccine we need for the future," said Osterholm. In 2012, Osterholm was part of a group that issued a report calling for prioritizing the search for a universal vaccine, which could be administered less often and remain effective on a wide range of influenza strains. . This is a major challenge, but Osterholm said we are getting closer and closer. "When we released this report, it was like screaming in the Grand Canyon. We are now seeing substantial investments in money and intelligence. "
Earlier this year, the National Institute of Allergy and Infectious Diseases released a strategic plan for the development of an effective universal influenza vaccine of at least 75%, providing protection against two of the major groups of influenza viruses. flu and providing protection for at least one year. and be suitable for people of all ages. Achieving this goal will take years and time is running out. It's only a matter of time before another pandemic appears. In this case, a universal vaccine is our best defense.
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