Limited effectiveness of flu vaccines

Limited effectiveness of flu vaccines

Effects of flu vaccines vary widely

Experts believe that this year's flu season will be particularly difficult. This is suggested by the first results, as the American Disease Control Agency Centers for Disease Control and Prevention (CDC) announced in a press release. The CDC therefore immediately recommends vaccination for prevention and immediate treatment with specific medication for high-risk patients.

So far this year’s season, the A H3N2 virus variant was the most common. It is a very aggressive virus, "which increasingly triggers severe flu diseases, hospital stays and deaths." In 2012/2013, 2007/2008 and 2003/2004, in which the H3N2 virus was predominant, the three flu seasons were the highest with mortality rates.
What increases the risk of a severe flu season is the realization that the viruses found in blood tests are mutated versions that are not covered by the flu vaccine. This means that the effectiveness against the mutants is reduced. In the case of the H3N2 mutant, 37-42 percent efficiency is currently assumed.

"It is too early to say for sure that the flu season will be difficult, but Americans should be prepared," said Tom Frieden, director of the CDC. "We can save lives with a three-point flu-fighting plan: vaccination, immediate treatment for people at high risk of complications, and preventive health care measures like staying at home when you're sick to reduce the spread of the flu. "

Flu vaccines are usually effective against 3 to 4 virus variants, even if they are only partially effective against some.

"Although the effectiveness of the flu vaccine against H3N2 is limited this year, we still strongly recommend getting vaccinated," said Joseph Bresee, M.D. of the CDC. “As has been shown in the past few years, vaccination does offer some protection against mutated virus strains. They also help protect against other strains of the flu virus that appear later in the season. ”

The main cause of the problem is the fact that the virus strains change regularly. However, since the vaccines have to be produced in advance, it is important for producers to estimate in advance of the flu season which strains of virus will be predominant in the season. If this then changes, the effectiveness of the vaccine can be reduced. Since H3N2 has been predominant in the southern hemisphere in recent years, it was still assumed in February that this virus would also dominate in the northern hemisphere during the flu season. Accordingly, the vaccine manufacturers have produced vaccines against this virus strain on the recommendation of the WHO. However, as it has now emerged, a related virus strain of H3N2 is spreading instead, against which the vaccine is only partially effective. According to the Robert Koch Institute, such developments have already occurred in the past and it is assumed that this can also be expected in the future. Ultimately, the race with the virus is one where you have to be lucky to win it: Luck in spring to make the right decision for the following autumn. (jp)

Image: Beßler / Havlena / pixelio.de

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