Exposure to harmless coronaviruses increases immunity against SARS-CoV-2

The immunity of the population to SARS-CoV-2, which is achieved through infection or vaccination, is crucial to overcome the COVID-19 pandemic. A new study, carried out by Swiss researchers, has observed that this immunity also increases in response to other harmless coronaviruses.

“People who have had strong immune responses to other human coronaviruses also have some protection against infection by SARS-CoV-2″, says Alexandra Trkola, director of the Institute of Medical Virology of the University of Zurich (UZH), who led the study.

In their study, the researchers used a specially developed assay to analyze antibody levels against four other coronavirus humans in 825 serum samples taken before the emergence of the SARS-CoV-2. They also examined 389 samples from donors infected with SARS-CoV-2. Combining these analyzes with computer-based models allowed the team to accurately predict how well antibodies would bind and neutralize invading viruses.

The researchers were able to show that people who got the SARS-CoV-2 had lower levels of antibodies against coronaviruses that cause common colds compared to uninfected people. Also, people with high levels of antibodies to harmless coronaviruses were less likely to have been hospitalized after contracting the virus. SARS-CoV-2.

“Our study shows that a strong antibody response to human coronaviruses increases the level of antibodies against human coronaviruses. SARS-CoV-2. Therefore, someone who has gained immunity to harmless coronaviruses is also better protected against serious infections by SARS-CoV-2″, says the researcher.

This type of immune response is known as cross-reactivity, and it also occurs with responses from T cells, the immune system’s additional line in defense against infection. People are only fully protected against the SARS-CoV-2 shortly after you have recovered from an infection or received an effective vaccine. This is when the levels of antibodies to the virus are still very high.

As these levels decline over time, infection is no longer prevented, but immune memory rapidly reactivates the body’s defenses, antibody production, and T-cell defense. “Of course, immune responses directed at the SARS-CoV-2 that are assembled by memory cells are much more effective than cross-reactive responses. But although protection is not absolute, cross-reactive immune responses shorten the infection and reduce its severity. And this is exactly what is also achieved by vaccination, much, much more efficiently “adds Trkola.

“If immunity to SARS-CoV-2 also offers some degree of protection against infection with other coronaviruses, we would be a significant step closer to achieving comprehensive protection against other coronaviruses, including any new variants.”, concludes. This idea is also supported by the fact that cross-reaction protection is not only based on antibodies, but most likely T cells as well.