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New evidence suggests that COVID-19 survivors who test positive for antibodies appear to be protected against reinfection for at least a few months.
Researchers found that having antibodies to the coronavirus put people at a 10 times lower risk of infection than those who tested negative for the antibody.
Plus, this protection lasted for at least 90 days after their first antibody test, and in some cases even longer.
The team, from the National Cancer Institute of the National Institutes of Health, the results are encouraging, but that more research is needed to determine how long survivors are protected and whether those protections are threatened by new variants of coronavirus spreading to across the United States.
A new study looked at 3.2 million antibody tests in January 2020 and August 2020 and found that 11.6% were positive for antibodies to the coronavirus, and the remaining 88.4% were negative. Pictured: A phlebotomist draws blood through a finger prick during a COVID-19 antibody test in Pico Rivera, Calif., February 2021
After at least 90 days, 0.3% of survivors were re-infected with COVID-19 compared to 3% of people who did not have antibodies (above, far right)
Antibody tests, also known as HIV tests, require blood to be drawn from a vein and can only be analyzed in a certified laboratory.
Some tests look for the IgG antibody, a protein that the body produces in the later stages of infection and can stick around for months, or even years, after a person heals.
Others try to detect the antibody, IgM, which is made by the body a few days after infection.
“ Data from this study suggests that people who test positive on a commercial antibody test appear to have substantial immunity to SARS-CoV-2, meaning they may be at lower risk of infection. future, ” said lead author Dr Lynne Penberthy. and Associate Director of the NCI Surveillance Research Program.
For the study, published in JAMA Internal Medicine, the team looked at data from more than 3.2 million U.S. adults who were tested for COVID-19 antibodies between January 2020 and August 2020.
Of the tests, 11.6%, over 378,000, tested positive for antibodies and the remaining 88.4%, over 2.8 million tested negative.
Over a follow-up period of at least 90 days, the researchers looked at the data to see how many people had tested positive for coronavirus infection.
The team noted that a positive antibody test within 30 days of the first test can be caused by someone still shedding the virus.
However, most viral shedding should stop after 90 days, so a positive result after three months would likely indicate a new infection.
They found that 0.3% of all people who tested positive for antibodies had been re-infected with COVID-19 compared to 3% of people who tested positive for the first time and did not have antibodies.
“ The study results are basically a 10-fold reduction, but I would have reservations about that, ” co-author Dr Douglas Lowy, senior deputy director of the National Institute, told CNN. cancer.
“In other words, it could be an overestimate of the reduction. This could be an underestimation of the reduction.
“For me the big message is: there is a reduction. The main thing to remember is that being positive for antibodies after natural infection is associated with partial protection against re-infection.
The authors say they are encouraged by the results, but that further studies are needed, including the duration of protection and whether it decreases over time.
Additionally, the study did not compare whether re-infected people had high or low levels of antibodies from their first infections.
“More research is needed to understand how long this protection lasts, who may have limited protection, and how patient characteristics, such as co-morbid conditions, may impact protection,” said Penberthy.
“We are nevertheless encouraged by this early discovery.
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