There is a growing body of evidence showing that people have lasting immunity after asymptomatic or mild COVID-19 infection.
A new study looked at antibody and T cell responses of a group healthcare workers with asymptomatic or mild covid-19 infection.
The results suggest that 89 percent of those healthcare workers had neutralizing antibodies against SARS-CoV-2 during 16-18 week follow-up after infection.
They also possessed T cells with the ability of detecting different parts of the virus.
However, these two levels of defence were not always coupled as some were showing neutralizing antibodies but not T cell immunity and vice versa.
Dr Joseph Gibbons, the study’s co-author, explained:
“Our study of SARS-CoV-2 infection in healthcare workers from London hospitals reveals that four months after infection, around 90 percent of individuals have antibodies that block the virus.
Even more encouragingly, in 66 percent of healthcare workers we see levels of these protective antibodies are high and that this robust antibody response is complemented by T cells which we see reacting to various parts of the virus.
This is good news.
It means that if you have been infected there is a good chance that you will have developed antibodies and T cells that may provide some protection if you encounter the virus again.”
Since the start of the pandemic researchers have been trying to find out how our body is protected against the coronavirus and how long this immunity will last.
The focus is mostly on B cells that produce antibodies and T cells responsible for making white blood cells to destroy infected cells.
This research reveals that some people didn’t produce T cells in response to the SARS-CoV-2 virus.
Notably, people with asymptomatic infection had less T cell immunity than those with classic COVID-19 symptoms.
However, both groups with symptomatic or asymptomatic infection had comparable neutralizing antibodies.
It seems even after mild infections people produce antibodies and T cells that recognize coronavirus epitopes.
Thus, vaccination provides the same effect in which our immune system would be able to detect the epitopes (a part of the antigen that binds to an antibody).
When a new variant appears the changes are not enough to stop the immune system from recognizing the epitopes, therefore the vaccine should work.
Dr. Corinna Pade, study co-author, said:
“Our study in asymptomatic and mild cases gives a positive insight into the durability of immunity to SARS-CoV-2 after four months of infection.
A remarkable number of around 90 percent of individuals have a joint force of strong antibodies that prevent the virus from entering, coupled with T cell responses to various parts of the virus to interfere with its survival.
This is an important find as mild or even no symptoms of COVID-19 are very common and representative of most infections in the community.
Such abundant immune responses also give hope for the long-lasting efficacy of vaccines.”
The study was published in the journal Science Immunology (Reynolds et al., 2020).