Men's blood has higher levels of a specific enzyme used by the novel coronavirus to invade cells than women, the findings of a major European research showed Monday - a result that could help shed light on why men are more vulnerable to COVID-19 infections.

The enzyme, called angiotensin-converting enzyme 2 (ACE2) is found in the kidneys, testis, heart, and other organs. In COVID-19, the respiratory illness caused by the novel coronavirus is believed to play a crucial part in the progression of the infection into the lungs.

The research of over 3,500 participants was published in the peer-reviewed publication European Heart Journal on May 10. In male subjects it found higher levels of ACE2 compared to females. The sample size was selective: all 3,500 subjects were senior citizens and had heart ailments.

The medical experts pointed out that research subjects who were given these medications did not have higher levels of ACE2, which adds to recent evidence that the vaccines do not increase the risk of coronavirus infection.

According to Dr. Iziah Sama, research co-author and faculty member at University Medical Center Groningen in the Netherlands, when they found that one of the strongest biomarkers, ACE2, was much higher in men compared to women, "I realized it had the potential to explain why men were more likely to die from COVID-19 than women."

ACE2 performs critical functions like helping the body digest and metabolise, however, in the case of SARS-CoV-2, it also acts as a latching site for the disease to cling on and work its way inside human cells.

According to the study, ACE inhibitors and ARBs are commonly recommended to patients with congestive heart failure, kidney disease or diabetes. Globally, the vaccine amounts to billions of dollars in prescription sales.

Adriaan Voors, a cardiology professor at the University Medical Center in The Netherlands who co-led the research, reportedly disclosed their work does not support the discontinuation of such medicines in COVID-19 patients.

Based on estimates, the pandemic has sickened over 4 million people worldwide and claimed the lives of 280,000. Infection and number of fatalities have shown that men are more likely to develop the virus than women, and experience severe or life-threatening complications.

Mean have also been found to be 2.5 times more likely to suffer from severe symptoms compared to women, a research released in April in the Lancet, showed.

This is likely the result of differences in social behavior such as increased smoking and poor hygiene compared to women, and sex hormones that affect responses in the immune system.