Healthcare workers were three times more likely to become infected during the Covid-19 pandemic compared to the general population, however re-infection rates appear very low, a new study has found.

Scottish researchers looked at 2,063 people who worked in a variety of healthcare roles.

Between May and September 2020, all were given blood tests to check for antibodies against Covid-19. The presence of these antibodies is considered a very accurate indication that someone has been infected with the virus. Researchers also recorded whether any participants developed an infection in the following months.

These results were compared with a randomly selected control group of blood samples taken by GPs during the same period of time.

The blood tests revealed that 300 (15%) healthcare workers had been infected with Covid-19, which was more than three times higher than the proportion of people infected in the general population.

Among these 300 workers, almost one in five (19%) did not realise they had ever had Covid-19 as they had been asymptomatic.

The highest rates of infection were found among dentists (26%), healthcare assistants (23%) and hospital porters (22%). The rate among administration staff was the same as the rate among doctors (21%).

While rates among people working in parts of the hospital where Covid-19 patients were being looked after were a little higher than those working in non-Covid areas (17% compare to 13.5%), the majority of infections occurred in staff who were not working directly with Covid patients. This suggests that transmission occurred between staff, or that infections were acquired in the community.

In the months following their blood tests, 39 workers developed a symptomatic Covid-19 infection, but only one of these was a worker who had previously tested positive. This equates to an 85% reduction in risk, which is similar to the protection provided by Covid-19 vaccines.

“We continued to monitor staff for up to seven months and found that having a positive antibody test gave 85% protection against a future infection. This is really good news for people who have already had Covid-19, as it means the chances of a second infection are very low,” explained Prof James Chalmers, a consultant respiratory physician from the University of Dundee.

The researchers plan to continue monitoring the workers to determine how long immunity lasts and how vaccination affects infection rates.

Details of the findings are published in the European Respiratory Society (ERS) journal, ERJ Open Research. According to ERS president, Prof Anita Simonds, the findings “show the high levels of Covid-19 infection among all healthcare workers”.

However, she added that staff working in critical care “who are likely to have been protected by using personal protective equipment (PPE) at all times, were not disproportionately affected”.