Study finds no link between influenza vaccine and COVID-19 risk

A new Cleveland Clinic study has found that receiving the influenza vaccine does not increase a person's risk for contracting COVID-19 or worsen associated morbidity or mortality. Published in the Journal of Clinical and Translational Science, the study shows the flu vaccine is the single most important intervention to help stay healthy this fall and winter.

Seasonal flu activity is unpredictable, and otherwise healthy people are hospitalized due to serious respiratory infection each year. This year, it's even more important to receive the flu vaccination to help prevent a twindemic of flu and COVID-19.

In this new study, a team of researchers led by Joe Zein, M.D. - a pulmonologist at Cleveland Clinic—analyzed more than 13,000 patients tested for COVID-19 at Cleveland Clinic between early March and mid-April of this year.

Comparing those who had received unadjuvanted influenza vaccines in the fall or winter of 2019 (4,138 patients) against those who did not received the vaccine (9,082 patients) revealed that influenza vaccination was not associated with increased COVID-19 incidence or disease severity, including risk for hospitalization, admission to the intensive care unit or mortality.

"Our findings suggest that we should proceed as usual with our vaccination strategy for global influenza this flu season," said Dr. Zein. "Getting the annual flu vaccine remains the best safeguard against the influenza virus—both for yourself and the people around you."

Since much is still unknown about the possible outcomes of concurrent SARS-CoV-2 (the virus that causes COVID-19) and influenza infection—including disease pathology and burden to the healthcare system—researchers and clinicians believe that the population's adherence to widespread and early flu vaccination while researchers continue to collect data will help to mitigate the risk of simultaneous viral infections and epidemics/pandemics.

"We have already seen the stress that COVID-19 can put on our hospitals and resources," said Dr. Zein. "While we're not yet sure how flu season will affect COVID-19 susceptibility and infections, we strongly advise people to get their influenza vaccines, both for their individual health and the collective health of our care systems."

This study is the latest to utilize data from patients enrolled in Cleveland Clinic's COVID-19 Registry, which includes all individuals tested at Cleveland Clinic for the disease, not just those that test positive. Cleveland Clinic was one of the first organizations to develop a data registry and biobank for the emergent disease. Data from the registry has already been used in several landmark COVID-19 studies, including those that have led to the development of models that can predict a patient's likelihood of testing positive for COVID-19 and being hospitalized due to the disease.