Study says flu vaccine can protect against severe effects of COVID-19

Washington: The influenza vaccine, which some take on an annual basis, is now found to be efferctive in reducing major Covid-19-caused effects such as stroke, sepsis, blood clots and other severe effects in patients.

The latest study of its kind made by the researchers from the University of Miami Miller School of Medicine, US, also found that patients with COVID-19 who had been vaccinated against the flu showed significantly less chances of visiting the emergency department (ED) and being admitted to the intensive care unit.

The conclusion of the study is an implied call to use the flu vaccine at least as a temporary, albeit partial protection against Covid-19 especially in the context of the low percentage of world population that has had the benefit of Covid vaccination.

"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, professor at the Miller School.

"My team has been able to observe an association between the flu vaccine and reduced morbidity in COVID-19 patients," said Singh, who conducted the study with lead authors Susan Taghioff and Benjamin Slavin.

The study, published in the journal PLoS One on August 3, analysed patient records from a number of countries, including the US, the UK, Germany, Italy, Israel and Singapore.

The researchers screened de-identified electronic health records on the TriNetX research database for more than 70 million patients to identify two groups of 37,377 patients.

Members of the first study group had received the flu vaccine two weeks and six 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 the flu.

The incidence of 15 adverse outcomes, including sepsis, strokes, deep vein thrombosis (DVT), emergency department visits and death, within 30, 60, 90 and 120 days of testing positive for COVID-19 were then compared between the two groups.

The analysis revealed that those who were not given the flu shot were significantly more likely (up to 20 per cent) to have been admitted to the ICU.

They were also significantly more likely to visit the emergency department (up to 58 per cent), to develop sepsis (up to 45 per cent), to have a stroke (up to 58 per cent) and a DVT (up to 40 per cent).

However, the flu vaccine was not proved to have reduced the risk of death among patients as death rates of those immunised was not reduced.

They were also able to calculate how many COVID-19-positive patients would need to receive an influenza vaccine to avoid one adverse outcome.

The team found that only 176 patients needed to have received a flu vaccine to prevent one ED visit within 120 days of testing positive for COVID-19.

Also, only 286 patients needed to have received their flu vaccine to prevent one case of sepsis.

For every 440 patients who were up to date on their flu shot, one ICU admission was prevented, according to the researchers.

Although it is not exactly known yet how the influenza vaccine provides protection against COVID-19, the researchers said, most theories speculate that the flu shot may boost the inherent immune system – inborn general defences that do not protect against any one specific illness.

The results, they said, strongly suggest that the flu vaccine may protect against several severe effects of COVID-19.

However, the researchers strongly recommend the annual flu vaccine not as a substitute for, but as complementary to the Covid-19.

The researchers added that more studies, in the form of randomised control trials, are needed to prove and better understand the possible link.

However, they said the flu shot could be used to help provide increased protection in countries with lesser penetration of the COVID-19 vaccine due to short supply.

"Continued promotion of the influenza vaccine also has the potential help the global population avoid a possible 'twindemic' -- a simultaneous outbreak of both influenza and coronavirus."

(With inputs from PTI)