Covid-19 variants may be less dangerous to vaccinated people and recovered patients than previously thought, according to researchers who found that the human body produces a strong cellular immune response to some of the most worrying new strains.

The US study, conducted by researchers at the La Jolla Institute for Immunology and the University of California, identified that T-cell responses in patients who had been vaccinated or previously infected were just as robust when faced with new variants of Covid-19 — including those first identified in Kent, Brazil, South Africa and California.

T-cells, which can “remember” past infections and kill pathogens if they reappear, are thought to have a big influence on how long people remain resistant to infection and disease. They come in several different types, including killer T-cells, helper T-cells and memory T-cells. B-cells, another essential type of white blood cell, produce antibodies.