The first European data on the effectiveness of influenza vaccine show a protection rate of between 32 and 43 percent against influenza A in primary care, and between 34 and 38 percent in hospitalized elderly. These results reinforce national and international vaccination recommendations.
An international study involving six European countries, including Spain through the Center for Biomedical Research in Network for Epidemiology and Public Health (CIBERESP), offers the first estimates of the effectiveness of the influenza vaccine. The data confirm that vaccination has been beneficial during the current campaign, from October 2018 to January of this year.
During this season there has been a predominant circulation of influenza A in Europe. 99.5% of the cases in all the studies combined were positive for this type of virus, with mixed circulation of subtypes A (H3N2) and A (H1N1) pdm09.
The results, published in Eurosurveillance, show effectiveness rates for all ages in primary care of 32 to 43 percent against influenza A in general, higher against the virus A (H1N1) pdm09 and lower compared to A (H3N2), the two subtypes that have circulated this season.
For the population of hospitalized older adults, the vaccine’s effectiveness has been estimated between 34 and 38 percent against influenza A in general, and slightly lower against influenza A (H1N1) pdm09.
In Spain, the provisional results of the vaccine’s effectiveness in primary care for this season for all ages are similar to the final results of last season, showing good protection against influenza A (H1N1) pdm09 (45 vs. 49 %), although it is suboptimal compared to A (H3N2).
According to Alin Gherasim, Clara Mazagatos and Francisco Pozo, of the National Center of Epidemiology and National Center of Microbiology of the Carlos III Health Institute, “this report shows that vaccination remains the most effective preventive measure against influenza, while at the same time supports the need for more effective interventions against subtype A (H3N2) in all age groups.”
“These results, therefore, reinforce national and international recommendations for influenza vaccination, especially in groups at high risk of complications from influenza, such as those over 64 years,” they added.
Results of six studies
In this article, studies from four countries were reported with estimates of vaccine effectiveness against influenza in primary care (United Kingdom, Denmark and Spain) and against hospital influenza (Denmark), and two multicenter reports of the European network I- MOVE that evaluates the effectiveness of the influenza vaccine in Europe each season. All included studies have a negative case-control design, with minimal differences in data collection and patient selection.
In all the included countries, random samples positive for influenza virus were selected for sequencing and the provisional results of vaccine effectiveness from these six studies were included in the GIVE (Global Influenza Vaccine Effectiveness) Report, which has served to inform about the situation of influenza vaccination in Europe at the meeting of the Committee for the Selection of Vaccine Strains of the World Health Organization (WHO), which took place from February 18 to 21, 2019.