Flu vaccine can protect against severe effects of COVID-19, study finds

A new study published in PLoS One suggests that the influenza vaccine may help safeguard individuals against COVID-19.

The retrospective cohort analysis found that patients with COVID-19 who had been vaccinated against influenza were less likely to visit an emergency department and be admitted to the ICU.

The researchers believe the findings indicate that influenza vaccine may reduce the risks of stroke, sepsis, and deep vein thrombosis (DVT) in patients with COVID-19.

Devinder Singh, MD, lead study author and professor of clinical surgery at the University of Miami Miller School of Medicine, and colleagues focused on patient records from the United States, the United Kingdom, Germany, Italy, Israel, and Singapore. The team screened and de-identified electronic health records on the TriNetX research database for more than 70 million patients to identify two groups of 37,377 patients who were matched for factors that could influence their risk of susceptibility to severe COVID-19, such as gender, ethnicity, smoking, and chronic diseases like diabetes, obesity, and chronic obstructive pulmonary disease.

Members of the first study group received the influenza vaccine 2 weeks and 6 months prior to being diagnosed with COVID-19. Those in the second group also had a positive COVID-19 diagnosis but were not vaccinated against influenza. The incidence of 15 adverse outcomes—including sepsis, stroke, DVT, and pulmonary embolism—was compared between the two groups within 30, 60, 90, and 120 days of testing positive for COVID-19.

Individuals who had not been vaccinated against influenza were up to 20% more likely to have been admitted to the ICU. In addition, they were up to 58% more likely to visit the emergency department, up to 45% more likely to develop sepsis, up to 58% more likely to have a stroke, and up to 40% more likely to develop DVT.

The researchers say the findings strongly indicate the influenza vaccine may prevent against several severe effects of COVID-19, and they urge people to receive COVID-19 vaccines in addition to their annual influenza vaccine.