T-cells give longer lasting immunity to Covid than antibodies, study shows

The results, described by experts as ‘reassuring’ give greater hope of generating an effective vaccine

CORONAVIRUS patients have cellular immunity for at least six months after infection even when antibodies are undetectable, new research shows, boosting hopes of long-term protection.

Scientists from Public Health England (PHE) and the University of Birmingham found that memory T-cells were present in everyone they tested.

The study comes just a week after research from Imperial College suggested that immunity may wane after just a few months.

But researchers found the immune cells persisted even when antibodies had fallen to such low levels that they could no longer be detected. It suggests that more people may have had the virus than previously thought, but had lost their antibody response, so it did not show up in surveillance testing. It also gives greater hope that vaccines will generate long-term immunity.

Previous studies have shown that Sars – a similar virus to coronavirus – can induce a T-cell response that lasts 10 years, but it was unknown whether a cellular response also happened in Covid.

Dr Shamez Ladhani, consultant epidemiologist at PHE and the study’s author, 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 i mpact on Covid vaccine development and immunity research.”

The study tested 100 NHS workers who had Covid but were asymptomatic or who had very mild disease. Researchers found that the T-cell response was 50 per cent higher in symptomatic people, which could mean asymptomatic individuals will not be as protected in the future, or simply that they are able to battle the disease more efficiently.

The authors said that even when antibodies appeared to have gone, they were probably still there in low numbers, and able to be triggered quickly, in the event of a new infection.

Prof Paul Moss, UK Coronavirus Immunology Consortium lead from the University of Birmingham, said: “To our knowledge, our study is the first in the world to show robust cellular immunity remains at six months after infection in individuals who experienced mild/ moderate or asymptomatic Covid-19.”

Dr Ladhani, said it was likely there was a cohort of people who catch coronavirus but never develop an antibody response and that testing T-cell immunity may be a better marker for finding out how many people have had the virus. Prof Charles Bangham, Chair of Immunology, at Imperial College London, said the results were “reassuring”.

The research has not yet been peer reviewed and was published on the preprint website biorxix.