Analysis of Influenza Vaccination Coverage and Vaccine Effectiveness in Population Aged 65 and Over in Ambulatory Medicine in France From 2016 to 2019: A Study Based on Real-World Data

OBJECTIVES: Influenza virus infection remains a major public health concern worldwide. Measuring vaccination coverage makes it possible to monitor adherence to recommendations by people at risk, and adapt in real time public health communication. We aimed to estimate vaccination coverage (VC) and vaccine effectiveness (VE) on THIN® database during the influenza seasons from 2015-2016 to 2018-2019.

METHODS: We formed four different season cohorts: All persons having visited a THIN® physician before and after each influenza season, having received a pharmacy delivery and aged 65 and over were included. Vaccination status for each cohort was obtained from pharmacy influenza vaccine delivery data. The outcome of influenza infection for VE was extracted from electronic medical records (EMR).

RESULTS: For 2015-2016, 2016-2017, 2017-2018 and 2018-2019 influenza seasons, a total of 239.188, 257.767, 251.970 and 250.914 participants were included respectively. VC was estimated at 48.30%, 54.13%, 49.95% and 55.7% and VE at 46.34% (IC, 43.25 % - 49.25 %), 49.95% (IC, 47.47 % - 52.30 %), 52.96% (IC, 50.62 % - 55.18 %) and 42.67% (IC, 39.59 % - 45.58 %) respectively. Comparing these results to Santé publique France (SpF) surveys and Sentinelles Network’s VE studies showed the robustness of THIN® France. The slight differences that we observed can be explained by the fact that THIN® data only include people who had consulted a general practitioner, regularly monitored by THIN® physicians would have better medical follow-up and better compliance, whereas SpF data come from the national health data system (SNDS), which combines data from health insurance (SNIIRAM), hospitals (PMSI) and statistics related to medical causes of death (BCMD).

CONCLUSIONS: THIN® data are available in near real time, the 20^th of the following month. Using THIN® data could be a reliable and efficient method to monitor flu vaccination campaign and flu outbreak each year.