A new study has found that those who are vaccinated against influenza are less likely to need critical medical care as the flu shot may reduce severe effects of COVID-19.

The study, titled "Examining the potential benefits of the influenza vaccine against SARS-CoV-2: A retrospective cohort analysis of 74,754 patients," was published in the peer-reviewed scientific journal PLoS One.

"Only a small fraction of the world has been fully vaccinated against COVID-19 to date, and with all the devastation that has occurred due to the pandemic, the global community still needs to find solutions to reduce morbidity and mortality," said senior study author Devinder Singh, MD, chief of plastic surgery, and professor of clinical surgery at the Miller School.

It analysed patient records from a number of countries, including the US, the UK, Germany, Italy, Israel and Singapore.

The study de-identified records of 73,346,583 patients were retrospectively screened.

Two cohorts of 37,377 patients, having either received or not received influenza vaccination six months–two weeks prior to SARS-CoV-2 positive diagnosis, were created using Common Procedural Terminology (CPT) and logical observation identifiers names and codes (LOINC) codes.

Adverse outcomes within 30, 60, 90, and 120 days of positive SARS-CoV-2 diagnosis were compared between the groups.

They were also significantly more likely to visit the emergency department, to develop sepsis, to have a stroke and a DVT.

The researchers said risk of death among patients immunised with the flu vaccine was not reduced.

Limitations include retrospective nature and its reliance on the accuracy of medical coding, the study said.

Future prospective controlled studies to validate these findings and determine if an increased emphasis on influenza vaccination will improve adverse outcomes in SARS-CoV-2-positive patients will be beneficial, it added.