Small study finds common coronavirus cold may help protect against COVID-19 infection

A new study involving several dozen participants has found evidence suggesting exposure to a common coronavirus cold may offer some protection against SARS-CoV-2, the virus that causes COVID-19.

Researchers from Imperial College London in the United Kingdom say their study examines how the presence of T-cells at the time of SARS-CoV-2 exposure can influence whether a person becomes infected.

T-cells are part of the body’s immune system and can help fight viral infections.

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Published in the journal Nature, the researchers say their findings provide a "blueprint for a second-generation, universal vaccine that could prevent infection from current and future SARS-CoV-2 variants, including Omicron."

They note that the study is limited by its small number of participants — 52 — most of whom were of white European ethnicity.

As well, first author of the study Rhia Kundu, from Imperial's National Heart and Lung Institute, says while an important discovery, it is only one form of protection that shouldn't be relied on alone.

Kundu added that the best way to protect oneself against COVID-19 is to be fully vaccinated, including getting a booster dose.

"Being exposed to the SARS-CoV-2 virus doesn't always result in infection, and we've been keen to understand why," Kundu said in a news release.

"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."

The study began in September 2020 and involved 52 people who lived with someone with a PCR-confirmed COVID-19 infection.

The participants did PCR tests at the start of their exposure, as well as four and seven days later, to see if they had developed any infection.

Blood samples taken within one and six days of exposure to the virus were then analyzed for levels of pre-existing T-cells, produced by previous common cold coronavirus infections, that would recognize SARS-CoV-2 virus proteins.

The researchers found "significantly" higher levels of cross-reactive T-cells in half of the people who did not become infected, compared to the other 26 who did.

The study says the T-cells targeted internal proteins in the SARS-CoV-2 virus as opposed to the spike protein located on the surface of the virus.

The researchers argue that, alongside existing vaccines which target the spike protein, new vaccines that target internal proteins could offer "long-lasting protection," since T-cell responses last longer than antibody responses.

"The spike protein is under intense immune pressure from vaccine-induced antibody which drives evolution of vaccine escape mutants," said Prof. Ajit Lalvani, senior author of the study and director of the National Institute for Health Research’s Respiratory Infections Health Protection Research Unit at Imperial.

"In contrast, the internal proteins targeted by the protective T-cells we identified mutate much less. Consequently, they are highly conserved between the various SARS-CoV-2 variants, including Omicron."

While the Omicron variant of COVID-19 is believed to be highly transmissible, evidence has suggested it is less likely to result in severe illness and hospitalization than the Delta variant, particularly for those who are fully vaccinated.