Covid-19 Antibodies May Protect Against Reinfection Later, Study Finds

A study, published Wednesday in the journal JAMA Internal Medicine, found that people who tested positive for Covid-19 antibodies had a lower risk of coronavirus infection compared to those who tested negative for antibodies.

“The study results are basically a 10-fold reduction, but I would have reservations about that. In other words, it could be an overestimate of the reduction. This could be an underestimate of the reduction, ”said Dr. Douglas Lowy, senior deputy director of the National Cancer Institute, author of the study.

Lowy added that people who have recovered from Covid-19 should always be vaccinated when it is their turn.

The researchers – from the National Cancer Institute and the companies LabCorp, Quest Diagnostics, Aetion Inc. and HealthVerity – looked at data from more than 3.2 million people in the United States who had taken a Covid-19 antibody test. last year between January and August. Of those tested, 11.6% tested positive for Covid-19 antibodies and 88.3% tested negative.

In follow-up data, researchers found that only 0.3% of those who tested positive for Covid-19 antibodies ended up testing positive for coronavirus infection later, beyond 90 days. While 3% of those with negative Covid-19 antibody test results were later diagnosed with coronavirus infection during the same period.

Overall, the study is observational and suggests an association between positive Covid-19 antibody test results and a lower risk of infection around 90 days later – but more research is needed. to determine a cause and effect relationship and for how long the antibody protection can last.

Lowy said more research is also needed to determine the risk of reinfection from one of the emerging variants of the coronavirus.

“Now that there are these worrying variants out there, what are the implications? The short answer is we don’t know,” Lowy said. He also stressed that people who test positive for antibodies should always be vaccinated against Covid-19.

It is already known that most patients who recover from Covid-19 have antibodies and reinfection appears to be rare so far – but it is still not clear how long antibody protection will last due to natural infection. Dr. Mitchell Katz of NYC’s Health + Hospitals healthcare system wrote in an editorial published alongside the new study in JAMA Internal Medicine.

“For this reason, vaccination against SARS-CoV-2 is recommended regardless of antibody status,” Katz wrote. SARS-CoV-2 is the name of the coronavirus that causes Covid-19.

“The duration of antibody protection provided by vaccines is also unknown,” he wrote. “Knowing how long protection with antibodies will last due to natural infection or vaccination is something only time will tell.”