Repeated Influenza Vaccination Helps Prevent Severe Flu in Older Adults

Getting the shot every year was about twice as effective

Repeated vaccination for influenza in older adults reduced the severity of the virus and reduced hospital admissions, according to new research published in the Canadian Medical Association Journal.

A team of Spanish researchers looked at the effect of repeated influenza vaccinations in the current and three previous seasons in people 65 years of age and older admitted to 20 Spanish hospitals in 2013-14 and 2014-15 to determine whether repeat vaccination reduced severe influenza.

They found repeated influenza vaccination was twice as effective in preventing severe influenza in people admitted to hospital for the virus, compared with nonsevere cases, and that this effect was consistent regardless of flu season, virus subtypes, or age of patient.

"Repeated vaccination for influenza was highly effective in preventing severe and fatal infection caused by influenza in older adults," write Dr. Itziar Casado and Dr. Jesús Castilla, Instituto de Salud Pública de Navarra, Pamplona, Spain, with coauthors.

The study adds to findings from previous research that shows influenza vaccination reduces severity of the illness.

"Because severe cases of influenza may be prevented by two mechanisms, the effectiveness of vaccination against severe influenza may be greater than that for mild cases, and the benefit of influenza vaccination may be greater than that estimated in previous studies. The prevention of severe and fatal infection caused by influenza was observed mainly in patients who were vaccinated in both the current and previous seasons, which reinforces the recommendation of annual vaccination for influenza in older adults," the authors conclude.

Source: CMAJ; January 8, 2018.