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LONDON: A small but key study from the UK has found that “cellular immunity” to the SARS-CoV-2 pandemic virus is present after six months in people who had mild or asymptomatic COVID-19, suggesting they might have some level of protection for at least that one time.
Scientists presenting the findings, out of 100 non-hospitalized COVID-19 patients in Britain, said they were “reassuring” but did not mean that people, in rare cases, could not be infected twice with the disease.
“While our findings cause us to be cautiously optimistic about the strength and duration of immunity generated after SARS-CoV-2 infection, this is only one piece of the puzzle,” said Paul Moss, professor of hematology at Britain’s University of Birmingham, who co-said the study.
“We still have a lot to learn before we have a full understanding of how immunity to COVID-19 works.”
Experts who were not directly involved in the study said their findings were important and would add to a growing body of knowledge about possible protective immunity against COVID-19.
The study, which has not yet been peer-reviewed but was published online at bioRxiv, tested the blood of 100 patients six months after they had mild or asymptomatic COVID-19. He found that while some of the patients’ antibody levels had decreased, their T-cell response, another key part of the immune system, remained strong.
“(Our) early results show that T cell responses may outlast the initial antibody response,” said Shame Ladhani, a consultant epidemiologist at Public Health England who co-led the work.
The study also found that the size of the T-cell response differed and was considerably larger in people who had had symptomatic COVID-19 than in those who had no symptoms when infected.
The researchers said this could be interpreted in two ways: it is possible that increased cellular immunity could provide better protection against reinfection in people who had symptoms, or that asymptomatic patients are better able to fight the virus without generating a great immune response.
“These results provide reassurance that although the antibody titer to SARS-CoV-2 may drop below detectable levels within a few months of infection, some degree of immunity to the virus can be maintained,” said Charles. Bangham, chair of immunology at Imperial College London.
“This … bodes well for the long term, both in terms of vaccine development and the possibility of long-term protection against reinfection,” said Eleanor Riley, professor of immunology and infectious diseases at the University of Edinburgh. . However, he emphasized that “we still don’t know if the people in this study are protected from reinfection.”
While more than 46 million people worldwide have been infected with COVID-19, confirmed cases of reinfection are so far very rare.
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