• Every day there is some new information about COVID-19 and the immunity against this deadly virus that comes to light.
• Now, a German study reveals that some people who did not have COVID-19 infection did demonstrate some immunity to the virus.
• How did these people get immunity without exposure?
• Did this prevent them from developing an active COVID-19 infection?

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A German study on immunity against COVID-19 in healthy adults

There is a new study published in Nature last month revealed that people with no COVID-19 infection still had some immunity against the deadly virus. But from where did these unexposed people get immunity?

German researchers studied 68 healthy adult people in Germany for immunity against coronavirus. These people were not exposed to the virus. But despite no exposure, 35% of them showed T-cell reactivity against COVID-19.

T-cells play a major role in body immunity against germs. They also are the cells that keep the memory of these infections.

This implies that the adults had previous contact with another type of ‘endemic’ and ‘less severe’ coronavirus and acquired this immunity at that time.

And it is this T-cell immunity that saves them from a new infection. This is cross-reactivity.

Also, read Is reinfection with COVID-19 real? What does it imply for the world?

More about this new study

The scientists collected blood samples from COVID-19 patients and also from healthy donors. All the study patients were from Germany. 83% of COVID-19 cases had the T-cells reactivity to coronavirus.

The healthy donors also had this but in a lesser number of cases. Despite finding these T-cells in the blood of cases of COVID-19 and also in some healthy adults, the researchers are not sure about the benefit and impact of these T-cells on the outcome of the illness.

Dr. Amesh Adalja, senior scholar at the Johns Hopkins University Center for Health Security is not a participant in this study.

However, he opines that more studies are required to confirm the role of T-cells in COVID-19 protection and disease outcome.

The expert opinions

Dr. Amesh said:

“It does appear in this study that there is a significant proportion of individuals that have this cross-reactive T cell immunity from other coronavirus infections that may have some impact on how they fare with the novel coronavirus. I think the big question is trying to jump from the fact that they have these T cells to understanding what the role of those T cells might be,”

Further, he explains:

“We know, for example, children and younger adults are relatively spared from the severe consequences of this disease, and I think that one hypothesis might be that the pre-existing T cells that exist may be much more numerous or more active in younger age cohorts than in older age cohorts,”

He adds:

“It’s clear though that the T cell presence doesn’t prevent people from getting infected, but does it modulate the severity of infection? That’s what it appears could be the case.”