COVID-19: Recovered patients may be immune to reinfection for five months, says study

A study conducted by the Public Health England (PHE) notes that a significant percentage of persons who have been infected with COVID-19 in the past may not contract the virus again for at least five months.

According to the SARS-CoV-2 Immunity and Reinfection Evaluation (SIREN) research led by Susan Hopkins, a professor and a senior medical advisor at PHE, over 80 percent of persons captured in the study were not reinfected.

The experts, however, cautioned that those with immunity may still carry the virus and risk transmitting it to others.

“PHE’s SIREN (SARS-CoV-2 Immunity and Reinfection EvaluatioN) study has performed regular antibody and PCR testing on 20,787 healthcare workers, including frontline clinical staff and those in non-clinical roles, from 102 NHS trusts since the study commenced in June. 6,614 of these participants tested positive for COVID-19 antibodies upon recruitment,” it reads.

“Of the 44 potential reinfections identified by the study, 2 were designated ‘probable’ and 42 ‘possible’, based on the amount of confirmatory evidence available. If all 44 cases were confirmed, it would represent an 83% rate of protection from reinfection, while if only the 2 ‘probable’ reinfections were confirmed, the rate would be 99%. Further research is ongoing to clarify this range.

“The study found that antibody protection after infection lasts for at least 5 months, on average, and scientists are currently studying whether protection may last for longer. This means that many people who contracted the disease in the first wave may now be vulnerable to catching it again.

“Both of the 2 ‘probable’ reinfections reported having experienced COVID-19 symptoms during the first wave of the pandemic, but were not tested at the time. Both patients reported that their symptoms were less severe the second time. None of the 44 potential reinfection cases were PCR tested during the first wave, but all tested positive for COVID-19 antibodies at the point of recruitment to the study.”

Speaking on the research effort, Hopkins noted that immunity from having COVID-19 is not “100 percent protective”, and maintained the need for strict adherence to COVID-19 protocols.

“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,” she said.

“This means even if you believe you already had the disease and are protected, you can be reassured it is highly unlikely you will develop severe infections but there is still a risk that you could acquire an infection and transmit to others. Now more than ever, it is vital we all stay at home to protect our health service and save lives.”