Not everyone exposed to COVID-19 develops an infection. A small study from the United Kingdom may help explain why.
The body's immune response to some common colds may offer some protection against COVID-19, according to scientists at Imperial College London.
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>Prior studies have found that T cells triggered by other coronaviruses – like those that cause the common cold – can recognize SARS-CoV-2, the coronavirus that causes COVID-19. This is the first study to find that those T cells play a role in whether a person becomes infected with COVID-19.
The researchers emphasized that people should not rely on a past cold to build immunity against COVID-19. The best protection remains vaccination. Rather, they said their findings could help scientists develop a COVID-19 vaccine that better protects against all COVID-19 variants, including omicron and others yet to emerge.
"The conclusion should not be that if you've had a common cold you don't need to worry about contracting COVID-19," study author Aljit Lalvani, of Imperial College London, told CBS News.
It is important to remember that not all colds are caused by coronaviruses, Lalvani added. Plus, the ability of T-cells to fight off infection wanes over time.
"These data should not be over-interpreted," Simon Clarke, at the University of Reading in the United Kingdom, told BBC News. "It seems unlikely that everyone who has died or had a more serious infection, has never had a cold caused by a coronavirus.
"And 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."
Clarke was not involved in the research.
The study included 52 people in the United Kingdom who had never been infected or vaccinated against COVID-19. But they all lived with someone who had a PCR-confirmed infection.
The researchers analyzed blood samples taken from all participants within 1-6 days of exposure. The 26 people who did not become infected had higher levels of T cells from prior cold infections that were capable of recognizing COVID-19 than the 26 people who became infected.
They also discovered that these T-cells target internal proteins within the coronavirus instead of the spike protein, which attaches to external cells.
Most COVID-19 vaccines create an immune response by replicating spike proteins. Creating a vaccine that targets both internal proteins responsible for virus replication and spike proteins could offer longer-lasting protection against COVID-19, the researchers said.
The internal proteins targeted by T-cells do not mutate as much as the spike protein, another benefit, Lalvani said.
Because the internal proteins remain similar across all known COVID-19 variants, new vaccines that target them would offer broader protection against all current and future variants, he said.
The findings were published in Nature Communications. The researchers acknowledged that because the study was small and included mostly participants of white European ethnicity, future research will be needed to confirm their findings.