WASHINGTON (BLOOMBERG) - Young adults previously infected with Covid-19 are still at risk of catching the disease again, according to a study of US military personnel that highlights the importance of vaccinating even those who have tested positive for the virus.

About 10 per cent of 189 people who had been infected once, most of them 18- to 20-year males, later became reinfected, according to a study of 2,346 US Marine Corps members published on Thursday (April 15) in The Lancet Respiratory Medicine journal. The study took place between May and November 2020.