Most people who have recovered from covid-19 have similar levels of immunity against future infection to those who received a coronavirus vaccine, a study by Public Health England found, offering early hope against fears of a short-lived immunity spurred on by reports of people catching the virus twice, though the researchers warn that those with immunity may still be able to carry and transmit the virus to others.
Naturally acquired immunity from a previous covid-19 infection provides 83% protection against reinfection when compared with people who have not had the disease before, government researchers found in a study of more than 20,000 healthcare workers.
The study, which has not yet been peer reviewed for rigor by other scientists, shows that this protection lasts for at least five months and is at a level just below that offered by vaccines from Pfizer-BioNTech (95%) and Moderna (94%) and significantly above that of the vaccine developed by the University of Oxford and AstraZeneca (62%), though manufacturers don’t know for how long this immunity lasts.
The figures suggest reinfection is relatively rare — occurring in fewer than 1% of the the 6,614 people who had already tested positive for the disease — though the scientists warned that while “those with antibodies have some protection from becoming ill with covid-19 themselves,” early evidence suggests that they can carry and transmit the virus to others.
“It is therefore crucial that everyone continues to follow the rules and stays at home, even if they have previously had covid-19, to prevent spreading the virus to others,” Public Health England wrote.
The study will continue to follow participants for another 12 months to determine “how long any immunity may last, the effectiveness of vaccines and to what extent people with immunity are able to carry and transmit the virus,” as well as investigate the highly-contagious new variant of coronavirus spreading across the U.K..
Professor Lawrence Young, a virologist and Professor of Molecular Oncology at Warwick Medical School in England, said an important takeaway from the study is that we don’t yet know how long antibody protection will last outside of the five month window. He said it is “possible that many people who were infected during the first wave of the pandemic may now be susceptible to re-infection.” Young said it will be interesting to see whether people previously infected with covid-19 and are subsequently vaccinated have “an even longer-lived protective immune response” and whether or not these findings hold true for the new virus variant currently spreading in the U.K..
What To watch For
The information gathered from reinfection cases could prove important as the pandemic progresses, especially when it comes to designing and implementing an effective vaccination program and deciding whether to ease lockdown measures. Whether or not those who are immune to serious illness are capable of transmitting the infection to others will be a crucial deciding factor.
What We Don’t Know
It’s not yet clear for how long the protection provided by vaccines last. This will have to be studied over time, as with this case of natural immunity, and is something manufacturers are already doing. Moderna believes their vaccine offers at least a year’s protection against disease. Whether or not this protection prevents individuals from infecting others will also need to be figured out.
384,784. That’s how many people have died from covid-19 in the U.S. since the pandemic began, according to Johns Hopkins university. According to CDC projections, this figure is set to grow 25% in the next three weeks. At the moment, more than 23 million people have contracted the disease in the U.S..