COVID-19 Immunity Could be Much Higher than Tests Suggest

Antiboidies against COVID-19 fade away quickly – this is what recent research has led us to believe. While this may be true, antibodies are not the only mediators of immunity against a virus. New research published in the preprint journal bioRxiv suggests that even individuals with no detectable antibodies may still form robust T cell memory.

T cells are a family of specialised white blood cells that can recognise virally -infected cells. When an infection is resolved, some T cells become memory cells that can rapidly reactivate when the same pathogen is encountered again.

In this study, researchers analysed blood samples from over 200 people, including many who had mild Covid symptoms or were asymptomatic. They found that COVID-19 specific T cells were present even in individuals with no detectable antibodies against the virus.

“One interesting observation was that it wasn’t just individuals with verified COVID-19 who showed T-cell immunity but also many of their exposed asymptomatic family members,” says Soo Aleman. “Moreover, roughly 30 per cent of the blood donors who’d given blood in May 2020 had COVID-19-specific T cells, a figure that’s much higher than previous antibody tests have shown.”

Immunity to COVID-19 is probably higher than tests have shown. (2020). Retrieved 2 July 2020, from https://news.ki.se/immunity-to-covid-19-is-probably-higher-than-tests-have-shown

The strength of this T cell response was ”akin to those observed in the context of successful vaccines”, suggesting that these memory cells may be sufficient to confer immunity.

Measuring T cell immunity is much harder than measuring antibodies, and is only performed in specialised laboratories. Measuring T cells is therefore unlikely to be a practical means of population-wide testing. Furthermore, while the memory T cell response may be robust, more studies are needed to confirm how long they persist and the extent of the protection they provide.

Nevertheless, these findings are encouraging, as they suggest that public immunity to COVID-19 is probably significantly higher than antibody tests have suggested.

Our results indicate that roughly twice as many people have developed T-cell immunity compared with those who we can detect antibodies in.

Immunity to COVID-19 is probably higher than tests have shown. (2020). Retrieved 2 July 2020, from https://news.ki.se/immunity-to-covid-19-is-probably-higher-than-tests-have-shown