London, May 25 (IANS): Health care workers were three times more likely to become infected during the Covid-19 pandemic compared to the general population, according to a study.

Around one in five of workers who were infected were asymptomatic and unaware they had Covid-19.

The study, published in ERJ Open Research, included a total of 2,063 health care staff, who were tested for antibodies against Covid-19, between May and September 2020. The presence of these antibodies is a very accurate indication that someone has been infected with Covid-19.

The blood tests showed that 14.5 per cent of the health care workers had been infected. This is more than three times higher than the proportion of people infected in the local population.

The highest rates of infections among the workers were in dentistry (26 per cent), health care assistants (23.3 per cent) and hospital porters (22.2 per cent). The rate among administrative staff was the same as that of doctors (21.1 per cent).

About 18.7 per cent did not think they ever had Covid-19 and were completely asymptomatic. The researchers say this is important since people without symptoms are likely to go to work and could potentially infect other people.

"A lot of attention during the pandemic has been around PPE for doctors and nurses but we found that dentists, health care assistants and porters were the staff most likely to test positive," said lead researcher Professor James Chalmers, a consultant respiratory physician from the University of Dundee, UK.

However, health care workers who had been infected were very unlikely to contract Covid-19 a second time in the following six months, the study showed.

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 per cent reduction in risk, which is similar to the protection provided by Covid-19 vaccines.

"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," Chalmers said. The team hopes to continue the research to see how long immunity lasts and how vaccination affects infections among health care workers.