Good news for the millions of people across the world still queuing for a COVID-19 vaccine. According to a new study, the flu vaccine may offer at least some protection against the worst symptoms of COVID-19. The researchers stress that this doesn’t mean that a flu shot can act as a replacement for a COVID-19 vaccine, which is your best bet against dodging the dangerous illness that forced the world to grind to a halt last year.
The researchers at the University of Miami Miller School of Medicine in the USA combed the TriNetX datasets that contain records on more than 70 million patients and identified two groups totaling 37,377. Patients from both groups were all, at some point, diagnosed with COVID-19, but those belonging to the first group had taken a flu vaccine between two weeks and six months before their diagnosis while those in the second group received no vaccine. The study period was between January 2020 and January 2021, when COVID vaccines weren’t widely available.
After accounting for factors that could affect the risk of severe COVID-19, including age, gender, smoking, and comorbidities such as obesity, diabetes, and chronic obstructive pulmonary disease, the researchers found that patients that had received a flu shot were less likely to become hospitalized or die after infection with the coronavirus. By accounting for these numerous lifestyle differences, we believe that there is a great deal of confidence that our two groups were very similar not only in terms of medical co-morbidities and diagnoses but also in terms of their access to healthcare.
Patients who didn’t get a flu vaccine were up to 20% more likely to have been admitted to the intensive care unit, as well as 58% more likely to visit the emergency department, 45% more likely to develop sepsis, and 58% more likely to have a stroke. The risk of death, however, was not reduced.
“This dataset has millions of patients and provides cohorts with very large sample sizes, which in turn helps to validate the statistics. Our analysis demonstrates a potential protective effect of influenza vaccination in SARS-CoV-2-positive patients against adverse outcomes within 30, 60, 90, and 120 days of a positive diagnosis. Significant findings include influenza vaccination mitigates the risks of sepsis, stroke, deep vein thrombosis (DVT), emergency department (ED) & Intensive Care Unit (ICU) admissions, thus suggesting a potential protective effect that could benefit populations without readily available access to SARS-CoV-2 vaccination,” Devinder Singh, the study’s senior author and a professor of plastic surgery at the University of Miami Miller School of Medicine, told ZME Science.
More research is required to confirm this link, preferably by prospective randomized clinical trials. Although no one knows for sure yet why the flu shot provides protection against COVID-19, one theory suggests that the protective effect is owed to an enhanced innate immune system. This general immune system responds to all kinds of pathogens, new or old, unlike the adaptive immune system that is primed against specific viruses.
Previously, researchers at the University of Georgia found that the measles, mumps, and rubella (MMR) vaccine may also offer protection against COVID-19 and may partly explain why children, who typically receive this vaccine around their first birthday, are largely immune to COVID.
Although close to 50% of the population of the USA and the European Union has been vaccinated with at least one dose against COVID, in developing nations that tally currently hovers at an underwhelming 1%. In this context, flu shots may be a temporary band-aid that the global health community can use to reduce morbidity and mortality due to the pandemic until proper vaccines become accessible to all in need. Besides, having a flu vaccine offers nothing but benefits.
“Our work is important not only because limited resources around the world continue to constrain access to the COVID vaccine, but also because it may help to address concerns about vaccine development. The flu vaccine has a much longer track record of safety, and this fact may help address the hesitancy reported in some people with respect to the COVID19 vaccine. The global population may benefit from influenza vaccination as it can dually act to prevent a coronavirus and influenza ‘twindemic’ which could potentially overwhelm healthcare resources,” Singh said.
However, Singh and colleagues emphasize that they “absolutely recommend the COVID19 vaccine, and in no way suggest the flu vaccine is a substitute to the proper COVID19 vaccine.”
The findings were presented at this week’s European Congress of Clinical Microbiology & Infectious Diseases (ECCMID).