Past COVID infection provides at least 5 months of immunity, study shows

London — Most people who have had COVID-19 have some immunity against catching it again for at least five months, according to a study by Public Health England. The U.K. government health agency’s research showed that someone who’s been infected is 83% less likely than someone with no previous infection to catch the coronavirus again over a five-month period.

The researchers noted, however, that someone who’s been infected may still be able to carry the virus and pass it on to others, even if they don’t get sick again. 

The period of partial immunity starts from when someone first becomes sick, according to the study.

The data comes from months of regular testing of health care workers, for both active infections and antibodies indicating past infection, carried out by Public Health England across the U.K. since June.

The agency warned that the findings suggest people who got sick with COVID-19 during the first wave of the pandemic in the spring might now be vulnerable to catching it again. It also warned that even if people who had already been ill might be protected themselves, preliminary data from the next stage of the study showed they still can carry high levels of the virus, and should still practice social distancing and wear masks to avoid infecting others.

“This study has given us the clearest picture to date of the nature of antibody protection against COVID-19 but it is critical people do not misunderstand these early findings,” Professor Susan Hopkins, senior medical advisor at Public Health England, said in a statement.

“We now know that most of those who have had the virus, and developed antibodies, are protected from reinfection, but this is not total and we do not yet know how long protection lasts. Crucially, we believe people may still be able to pass the virus on.”

“Now more than ever it is vital we all stay at home to protect our health service and save lives,” stressed Hopkins.

Scientists will continue to monitor people involved in the study for a year to see how long immunity lasts, how effective the vaccines are, and to confirm whether people who’ve had the virus are still able to pass it to others. 

They will also work to determine if prior infection with COVID-19 can protect someone from becoming ill with the new, highly infectious variant of the virus that emerged late last year in southern England.

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