Study Finds Flu Shots Protect Against Some Severe COVID-19 Symptoms


Individuals with COVID-19 who had not had a flu shot were up to 20% more likely to be admitted to the ICU and were up to 58% more likely to visit the emergency department.

The flu vaccine may provide some protection against severe symptoms of COVID-19, with a new study finding lower intensive care unit (ICU) admissions, sepsis, and stroke rates.

An analysis of patient data presented at the European Congress of Clinical Microbiology & Infectious Diseases found that the annual flu shot reduces the risk of stroke, sepsis, and deep vein thrombosis (DVT) in patients with COVID-19. Individuals with COVID-19 who had been vaccinated against the flu were also less likely to visit emergency departments (ED) and to be admitted to the ICU.

Several studies have found similar results, although this is the largest study of its kind, according to the authors. The research team screened de-identified electronic health records of more than 70 million patients worldwide and identified 2 groups of 37,377 patients.

“Having access to real-time data of millions of patients is a powerful research tool,” said Devinder Singh, MD, senior author of the study, in a press release. “Together with asking important questions, it has allowed my team to observe an association between the flu vaccine and lower morbidity in COVID-19 patients.”

The 2 groups were matched for factors that could impact their risk of severe COVID-19, including age, gender, ethnicity, smoking, and health problems such as diabetes, obesity, and chronic obstructive pulmonary disease. Members in the first group had received the flu vaccine between 2 weeks and 6 months before being diagnosed with COVID-19. Those in the second group also had COVID-19 but had not received flu vaccines.

Researchers analyzed the incidence of 15 adverse events (AEs): sepsis; stroke; DVT; pulmonary embolism; acute respiratory failure; acute respiratory distress syndrome; arthralgia or joint pain; renal failure; anorexia; heart attack; pneumonia; ED visits; hospital admission; ICU admission; and death. Rates of these AEs within 120 days of testing positive for COVID-19 were compared between the 2 groups.

According to the study, those who had not had a flu shot were up to 20% more likely to have been admitted to the ICU. They were also up to 58% more likely to visit the ED, up to 45% more likely to develop sepsis, up to 58% more likely to have a stroke, and up to 40% more likely to have DVT. The risk of death was the same across both groups.

Although the researchers said they do not know exactly how the flu vaccine protects against these COVID-19 affects, most theories believe it boosts the innate immune system, including general defenses that are not tailored to any specific illness. However, they said more research is needed to better understand the possible link.

These findings could be important for regions that have struggled to vaccinate people against COVID-19, and in countries that have not yet received doses of the vaccines. Although production and distribution of COVID-19 vaccines increase daily, the study authors said some countries are not expected to vaccinate large numbers of their populations until the beginning of 2023, despite the proven importance of immunizations. Offering flu vaccines could help provide increased protection, according to the study.

The findings could also be significant for individuals hesitant to receive COVID-19 vaccines, according to researcher Susan Taghioff.

“Despite this, the influenza vaccine is by no means a replacement for the COVID-19 vaccine, and we advocate for everyone to receive their COVID-19 vaccine if able to,” Taghioff said in the press release.


Flu jab protects against some of the severe effects of COVID-19, including. EurekAlert. July 11, 2021. Accessed July 12, 2021.

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