Abstract
The explanation of the potential interaction between the influenza vaccine and SARS-CoV-2 infection is urgently needed in the public health. The objective of the study is to compare the occurrence of positive SARS-CoV-2 IgG and IgM tests in subjects with and without recent (last year) seasonal influenza vaccinations. In a cross-sectional study located in three large towns of Silesian Voivodeship (Poland), we studied 5479 subjects in which 1253 (22.9%) had a positive anti-SARS-CoV-2 IgG test and 400 (7.3%) had a positive anti-SARS-CoV-2 IgM test. Seasonal influenza vaccination remains an independent factor protecting against positive IgG tests (OR = 0.68; 0.55–0.83). The effect is not apparent with IgM antibodies. The obtained results confirmed that the serological status of SARS-CoV-2 infection depends on vaccination against seasonal influenza.
Highlights
Influenza and COVID-19 are respiratory viral illnesses that may present with similar symptoms, and coinfections can result in more serious complications with fatal outcomes [1]
Humoral immune responses to SARS-CoV-2 are mediated by antibodies that are directed to viral surface proteins, mainly the spike glycoprotein and the nucleocapsid protein, and such antibodies neutralize the viral infection of human cells [5]
In the EPICOVID19 questionnaire study conducted in Italy, influenza vaccinations were associated with a decreased probability of a SARS-CoV-2-positive test in the younger participants (OR = 0.85, 95% CI, 0.74–0.98) [13]
Summary
Influenza and COVID-19 are respiratory viral illnesses that may present with similar symptoms, and coinfections can result in more serious complications with fatal outcomes [1]. Both viruses, (i.e., influenza and the novel coronavirus) depend on a viral RNA polymerase and use surface proteins to infect the host [2]. Discussion about the potential benefits or risks of influenza vaccination on the risk of COVID-19 persists, there is no clear scientific explanation for a possible effect of influenza vaccination on the risk of SARS-CoV-2 infection [7,8,9,10,11]. Other authors have posited the minimum number of influenza vaccinations needed to obtain herd immunity [14]
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