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Immunity against COVID-19 is a complex picture, and while there
is evidence of waning antibody levels six months after
vaccination, T-cells are also believed to play a vital role in
providing protection.
The study, which began in September 2020, looked at levels of
cross-reactive T-cells generated by previous common colds in 52
household contacts of positive COVID-19 cases shortly after
exposure, to see if they went on to develop infection.
It found that the 26 who did not develop infection had
significantly higher levels of those T-cells than people who did
get infected. Imperial did not say how long protection from the
T-cells would last.
"We found that high levels of pre-existing T cells, created by
the body when infected with other human coronaviruses like the
common cold, can protect against COVID-19 infection," study
author Dr Rhia Kundu said.
The authors of the study, published in Nature Communications,
said that the internal proteins of the SARS-CoV-2 virus which
are targeted by the T-cells could offer an alternative target
for vaccine makers.
Current COVID-19 vaccines target the spike protein, which
mutates regularly, creating variants such as Omicron which
lessen the efficacy of vaccines against symptomatic infection.
"In contrast, the internal proteins targeted by the protective
T-cells we identified mutate much less," Professor Ajit Lalvani,
co-author of the study, said.
"Consequently, they are highly conserved between the various
SARS-CoV-2 variants, including Omicron. New vaccines that
include these conserved, internal proteins would therefore
induce broadly protective T cell responses that should protect
against current and future SARS-CoV-2 variants."
(Reporting by Alistair Smout; editing by Philippa Fletcher)
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