People testing negative for coronavirus antibodies may still have some immunity, a study has suggested.

For every person testing positive for antibodies, two were found to have specific T-cells which identify and destroy infected cells.

Some were blood donors while others were tracked down from the group of people first infected in Sweden, mainly returning from earlier affected areas like northern Italy.

This could mean a wider group have some level of immunity to Covid-19 than antibody testing figures, like those published as part of the UK Office for National Statistics Infection Survey, suggest.

Much of the discussion around Covid-19 immunity has focused on antibodies - Y-shaped proteins which act like "missiles shooting down a target", assistant Prof Buggert explained.

If antibodies fail to neutralise the virus, it can enter your cells and turn them into virus-making factories.

This was not observed in the Karolinska study, which found the sicker the patient, the higher the level of antibodies and T-cells they appeared to produce