Positive association between COVID-19 deaths and influenza vaccination rates in elderly people worldwide

Abstract

Background The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is an ongoing global health crisis, directly and indirectly impacting all spheres of human life. Some pharmacological measures have been proposed to prevent COVID-19 or reduce its severity, such as vaccinations. Previous reports indicate that influenza vaccination appears to be negatively correlated with COVID-19-associated mortality, perhaps as a result of heterologous immunity or changes in innate immunity. The understanding of such trends in correlations could prevent deaths from COVID-19 in the future. The aim of this study was therefore to analyze the association between COVID-19 related deaths and influenza vaccination rate (IVR) in elderly people worldwide. Methods To determine the association between COVID-19 deaths and influenza vaccination, available data sets from countries with more than 0.5 million inhabitants were analyzed (in total 39 countries). To accurately estimate the influence of IVR on COVID-19 deaths and mitigate effects of confounding variables, a sophisticated ranking of the importance of different variables was performed, including as predictor variables IVR and some potentially important geographical and socioeconomic variables as well as variables related to non-pharmaceutical intervention. The associations were measured by non-parametric Spearman rank correlation coefficients and random forest functions. Results The results showed a positive association between COVID-19 deaths and IVR of people ≥65 years-old. There is a significant increase in COVID-19 deaths from eastern to western regions in the world. Further exploration is needed to explain these findings, and additional work on this line of research may lead to prevention of deaths associated with COVID-19.

Examining the potential benefits of the influenza vaccine against SARS-CoV-2: A retrospective cohort analysis of 74,754 patients

“…In a large scale study of over 2,000 counties in the United States, Zanettini et al demonstrated a potential protective effect of influenza vaccination on SARS-CoV-2 mortality [ 29 ]. Conversely, Wehenkel et al performed a macro-scale study of association between influenza vaccination rate and SARS-CoV-2 deaths in an examination of over 500,000 patients across 39 countries [ 30 ]. This study showed a positive association between COVID-19 deaths and influenza vaccination rates in elderly people 65 years of age and older.…”

Influenza Vaccination and Health Outcomes in COVID-19 Patients: A Retrospective Cohort Study

“…However, an Italian study [ 8 ] of a sample of healthcare workers found no evidence of a relationship between the influenza vaccine and either a COVID-19 diagnosis or a positive SARS-CoV-2 serology test in this group. Furthermore, Wehenkel C [ 9 ] reported a positive correlation between COVID-19 deaths and influenza vaccination in people ≥65 years-old, although the journal’s editors reminded readers that correlation does not necessarily imply causation. By contrast, a 2020 non-systematic review of the published, pre-print, and gray literature [ 10 ] concluded that high rates of coverage by the influenza and 23-valent pneumococcal polysaccharide vaccines has the potential to not only reduce the burden of the targeted diseases but to also prevent a proportion of COVID-19 morbidity and mortality.…”

Absence of association between 2019‐20 influenza vaccination and COVID‐19: Results of the European I‐MOVE‐COVID‐19 primary care project, March‐August 2020

“…An article on influenza vaccination increasing the risk of seasonal coronaviruses 6 has fuelled these claims, despite its results having been refuted 7 . Additionally, ecological studies correlating influenza vaccination uptake rates and COVID‐19 mortality, published in scientific journals as articles or rapid responses to articles sustain these hypotheses 8,9 …”