Vaccination can reduce the severity of influenza in vaccinated but still infected patients

The study, published in the scientific journal Eurosurveillance, also counts on the participation of researchers from the Public Health Agency of Catalonia, the Biomedical Research Institute of Lleida and the Public Health Agency of Barcelona.

Every year, between 5% and 20% of the world's population contract the flu, which causes about 3 to 5 million serious cases and between 300,000 and 500,000 deaths worldwide. The new study badyzes the effectiveness of influenza vaccines in reducing the most serious effects of influenza: ICU admissions and deaths of patients whose vaccine did not prevent them from infecting it. To do this, the researchers studied all severe cases of influenza in twelve Catalan hospitals during the influenza seasons 2010-2011 and 2015-2016, a period during which 1727 out of 18 patients entered the hospital. 591 were ICU admissions and 223 resulted in deaths.

The results show that among ICU admissions and deaths, vaccination was less common (21.2% of cases) than the rest of patients with mild symptoms, of which 29.7% were vaccinated. Therefore, the effectiveness of influenza vaccination to prevent ICU admissions or death among the total number of people hospitalized for influenza was 23%, and in particular 44% for the group of people 65 years old. "We should add the effectiveness of the vaccine to prevent influenza at these percentages. These data highlight the need for a flu shot for each season for people who are more likely to show severe types of influenza." , such as people over 65 and people with other diseases, for whom the flu vaccine was not enough to prevent the infection from appearing, "note the authors.

In the study, the researchers noted that these results would be attributable to the role played by the immune system. "People who had previously been infected with the virus or had received influenza vaccines would at least benefit from the pre-existing cross-memory of cytotoxic T lymphocytes, which would reduce the severity of the infection, even without antibodies. protectors, "they conclude.

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