Covid-19 antibodies may later protect against reinfection, research suggests

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

“The results of the study are actually a 10-fold reduction, but I would have reservations about that. In other words, it could be an overestimation of the reduction. It could be an underestimate of the reduction,” said Dr. . Douglas Lowy, chief assistant director of the National Cancer Institute, who was an author on the study.

Lowy added that people who have recovered from Covid-19 should still get vaccinated when it comes their turn.

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

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

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

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

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

It is already known that most patients recovering from Covid-19 have antibodies and reinfection seems to be rare so far – but it is still unclear “how long antibody protection will last because of a natural infection,” Dr. Mitchell Katz of NYC. The Health + Hospitals health system wrote in an editorial that appeared 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.

“How long vaccine antibody protection will last is also not known,” he wrote. “Knowing how long protection will last with antibodies due to natural infection or vaccination, only time will tell.”