COVID-19 Severity in Europe and the USA: Could the Seasonal Influenza Vaccination Play a Role?

Abstract

The factors affecting COVID-19 infection risk and disease severity have been widely discussed. The role that seasonal influenza vaccinations may play is generally not included in the debate. We performed an analysis investigating a possible link between the vaccination coverage rate (VCR) in the elderly (≥ 65 years of age) and COVID-19 infection risk or disease severity. Data from Europe (country-wise) and the USA (state-wise) were investigated separately. We found statistically significant positive correlations between the VCR and reported COVID-19 incidence, as well as mortality for Europe and the USA. A statistically significant positive correlation was also found between the VCR and the COVID-19 case fatality rate (CFR) for Europe. For the USA, the VCR/CFR correlation was not statistically significant. Our analysis indicates that receiving seasonal influenza vaccination(s) in the past might be an additional risk factor for the elderly in terms of enhanced susceptibility to infection with SARS-CoV-2 and higher likelihood of a lethal outcome in case of infection. More research about this possible risk factor is urgently needed.

Note: Funding: The study was self-funded

Declaration of Interest: We declare no conflict of interest

Keywords: COVID-19, SARS-CoV-2, seasonal influenza vaccination, vaccination-associated virus interference