Anti-virus cells still protect us 6 months after infection

COVID patients are left with a form of immunity for at least six months after infection, a study has found.

This raises hope that virus survivors have long-term protection against reinfection.

Every patient in the study tested half a year on had responsive Tcells – a key part of the immune system. Until now, scientists have mostly focused on antibodies, which neutralise a virus before it enters the body’s cells.

But the study led by Public Health England and the University of Birmingham found antibody levels fell rapidly in many patients a few months after recovery.

In comparison, T-cells – which target and destroy cells that are already infected by the virus – seem to be long-lasting. Even those patients whose antibody levels had fallen so far that they were no longer detectable were found to have a T-cell response six months later.

Study author Dr Shamez Ladhani, an epidemiologist at PHE, said: ‘Cellular immunity is a complex but potentially very significant piece of the Covid-19 puzzle.

‘Early results show that T-cell responses may outlast the initial antibody response, which could have a significant impact on Covid vaccine development and immunity research.’

Dr Ladhani said T-cell immunity may be a better marker for finding out how many people have had the virus than antibody levels. For the study, researchers tested 100 NHS workers who developed Covid but either had no symptoms or only a mild illness.

They found that the worse the symptoms, the greater the immune response.

Professor Paul Moss, a haematologist at the University of Birmingham, described the data as ‘reassuring, potentially even encouraging’.

But he stressed that the team had not tested the link between T-cells and reinfection with exposure to the virus. Nevertheless, there have been only a few reinfections among the millions who have had the virus worldwide.

The study has not yet been peerreviewed or published in a journal.