Scientists say a previous infection from the common cold could help protect against COVID-19 — but don't ditch getting a vaccine

• Immunity from other coronaviruses, like a cold, can offer some protection against COVID-19, a study found.
• The T cell immune response recognizes parts of the virus that are similar, the study authors said.

Scientists say a previous infection from a common cold could offer some protection against COVID-19, but warned that it shouldn't stop people from getting vaccinated.

A small study, led by researchers at Imperial College London and published in Nature Monday, found that protective cells in the body, called T cells, influenced whether or not people caught COVID-19 when a household member was infected.

"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," Dr. Rhia Kundu, first author of the study, said in a statement.

T cells work by attacking the inner parts of the virus, rather than the component that attaches to human cells, which existing vaccines and treatments target.

The findings are promising for some all-in-one coronavirus boosters currently in development that target internal parts of the virus, which are less likely to mutate. Those vaccines aim to protect against a number of coronaviruses or variants in one shot, including viruses that haven't yet crossed from animals to humans, as Insider previously reported.

Ajit Lalvani, senior study author, said the latest findings were "an important discovery", but cautioned a previous common cold infection only offered one form of protection.

"I would stress that no one should rely on this alone. Instead, the best way to protect yourself against COVID-19 is to be fully vaccinated, including getting your booster dose," Lalvani, director of the National Institute for Health Research Respiratory Infections Health Protection Research Unit at Imperial, said in a statement.

Simon Clarke, associate professor in cellular microbiology at the University of Reading, said the data added to understanding of how the body fights COVID-19, and suggested new vaccines might benefit from targeting other parts of the virus. But he added that the findings shouldn't be "overinterpreted".

"It seems unlikely that everyone who has died or had a more serious infection, has never had a cold caused by a coronavirus," Clarke said in a statement to the Science Media Center on Monday.

"It could be a grave mistake to think that anyone who has recently had a cold is protected against COVID-19, as coronaviruses only account for 10-15% of colds. Similarly, there is no measurement of how much protection the reported effect gives people and a link is only hinted at, it has not been proven conclusively," Clarke added.

To get the results, the researchers took blood samples from 52 people living with a person with COVID-19 and found "significantly higher" levels of T cells that could fight both a common cold and COVID-19 in the 26 people who didn't catch COVID-19, compared to the 26 participants who did, the study authors said.

Mala Maini, a professor of viral immunology at University College London, said in a statement to the Science Media Center on Monday, that it was likely household members testing negative in the study had a "transient abortive infection" that didn't get picked up by lab tests rather than completely resisting infection. "T cells recognize viral fragments once they have got into cells, rather than blocking infection as antibodies can," she said.

The research was funded by the UK's NIHR Health Protection Research Unit in Respiratory Infections and the Medical Research Council.