What Are T Cells? Universal COVID Vaccine Could Be on Horizon Thanks to Common Cold Immunity

Immune system T cells from previous illnesses could help people fight off COVID-19, a new study has found, pointing to a new generation of potential vaccines.

The study, carried out by researchers at Imperial College London, suggests that these existing cells which people acquire from other human coronaviruses (such as the common cold) can protect against COVID-19 infection, according to its lead author Dr Rhia Kundu.

However, Kundu added in an Imperial College London press release: "While this is an important discovery, it is only one form of protection, and 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."

In addition, Dr Simon Clarke, a professor of cellular microbiology at the University of Reading, told the BBC that it would 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 percent of colds."

In any case, the study started in September 2020 and looked at 52 people who had been exposed to COVID-19 through a household contact.

The participants then had blood samples taken within one to six days of exposure, enabling the researchers to look at their pre-existing T cells from common cold infections.

They found that of the 52 people studied, 26 who did not become infected had significantly higher T cell counts than those who did become infected.

Professor Ajit Lalvani, senior author of the study, and director of the NIHR Respiratory Infections Health Protection Research Unit at Imperial College London, said in the press release: "Our study provides the clearest evidence to date that T cells induced by common cold coronaviruses play a protective role against SARS-CoV-2 infection."

A new type of vaccine that makes use of these cells could be universal and prevent infection from current and future SARS-CoV-2 variants, according to the press release.

What Are T Cells?

T cells are a type of white blood cell and are an essential part of the immune system since they help fight viruses.

When it comes to COVID-19, these T cells provide protection by attacking proteins within the virus, whereas current COVID-19 vaccines do not work this way.

It is thought that T cells may provide longer-lasting protection against COVID-19 than their protective counterparts, antibodies.

Marc Hellerstein, a professor at the University of California Berkeley's Department of Nutritional Sciences and Toxicology, wrote in the Elsevier Vaccine X journal in August 2020 that "in severe acute respiratory syndrome, only 50 percent of survivors had detectable antibodies at three years and none had antibodies or B-cell responses to SARS-CoV-1 at 6 years, while virus-specific T cells remain at 6-17 years."

Indeed, concern has been raised in recent times over the waning effectiveness of current COVID-19 vaccines and the potential need for more boosters.

The Imperial College London team note that its study had the limitation of being small and participants were 88 percent of white European ethnicity, meaning demographic factors could not be modelled.

The study, entitled "T cells from common colds cross-protect against infection with SARS-CoV-2", was published in the journal Nature Communications on January 10, 2022.

COVID vaccine
A photo shows a health worker holding a COVID-19 vaccine in Aurora, Colorado, in December 2020. Current coronavirus vaccines work but their effectiveness wanes over time. Michael Ciaglo/Getty