Flu Vaccine Protects Against COVID-19, Says Study

Source: shutterstock

According to a large-scale study, the flu vaccine protects against the development of adverse outcomes in COVID-19 positive patients.

In recent months, multiple studies have come forward suggesting a link between the flu vaccine and COVID-19. In March, researchers at Michigan Medicine found that people vaccinated with the flu vaccine had lower chances of testing positive for the novel coronavirus and developing a severe infection. However, it is unclear as to how this protective effect comes about. Some suggest that the vaccine flu shot likely increases the number of natural killer cells in the body; its levels are often decreased in moderate to severe COVID-19. 

In an effort to explore the flu vaccine’s protective effect further, researchers at the University of Miami Miller School of Medicine conducted a retrospective study. They aimed to assess the vaccine’s effect in reducing the critical adverse outcomes in COVID-positive patients.

Having access to the real-time data of millions of patients is an incredibly powerful research tool. Together with asking important questions, my team has been able to observe an association between the flu vaccine and reduced morbidity in COVID-19 patients.

Dr. Devinder Singh, senior study author

Using electronic medical records (EMRs) from several countries including the UK, Israel, Germany, Italy, and the US, the team analyzed data from 74,754 patients. Thus, making this the largest study of its kind. They published their findings in the journal PLoS ONE.

Increased Chances of DVT, Sepsis, and Other Severe Outcomes

Researchers divided the patients into two groups of 37,377 patients. The first study group included those who had received a flu vaccine two weeks to six months prior to their positive COVID-19 diagnosis. The other group included patients who had tested positive but had never received the flu vaccine. The two groups were then compared for adverse outcomes within 30, 60, 90, and 120 days of receiving their diagnosis. The team assessed for 15 adverse outcomes including sepsis, deep vein thrombosis (DVT), stroke, renal failure, ICU admission, and death.

Results showed a greater risk of severe effects in the unvaccinated group. Not only did the group had more ICU admissions, but also were more likely to develop sepsis or have a stroke. However, the study did not find a link between the flu vaccine and fewer deaths among COVID-positive patients.

Continued promotion of the influenza vaccine also has the potential help the global population avoid a possible ‘twindemic’—a simultaneous outbreak of both influenza and coronavirus.

Susan Taghioff, study author

The results of the study suggest the benefits of the flu vaccine in protecting against severe effects of COVID-19. Therefore, the study authors recommend flu vaccines, even in those who have already received a COVID-19 vaccine.


Taghioff SM, Slavin BR, Holton T, Singh D (2021) Examining the potential benefits of the influenza vaccine against SARS-CoV-2: A retrospective cohort analysis of 74,754 patients. PLoS ONE 16(8): e0255541.DOI: 10.1371/journal.pone.0255541


Please enter your comment!
Please enter your name here