COVIS-19 Survivors have estimated 10 fold increase in protection--study

COVID-19 survivors tend to have a roughly tenfold increase in protection against the virus, according to a government-funded study published Wednesday.

Why it matters: There have been some documented cases of reinfection leading to concern survivors don't gain any immunity. While there remain questions on how much or how long immunity lasts and what the impact of variants will be, this large set of observational data bolsters evidence there's some protection.

The latest: The study, published in JAMA Internal Medicine, examined commercial SARS-CoV-2 antibody test data from 3.2 million U.S. patients from Jan. 1 and Aug. 23, 2020.

• Out of those who had tested antibody-negative initially and were later tested for active infection, they found 3% were positive for SARS-CoV-2 90 or more days later.

• Out of those who were antibody-positive initially and were later tested for active infection, they found only 0.3% were positive for SARS-CoV-2 90 or more days later.

• "There's a tenfold decrease, which is essentially a 90% reduction in risk for people who are antibody positive," says Doug Lowy, co-author and deputy director of the National Cancer Institute, which conducted the study.

• "It's something that has been hypothesized for a long time, but our study is by far the largest study to look at this, especially in the United States," Lowy says.

Caveat: Because the study examines real-time data and was not done in a clinical trial setting, there are could be "confounders," or distorting factors, that affect results, Lowy points out. This means the tenfold protection is a rough average — in actuality, "maybe it's a threefold difference, and maybe it's a twentyfold difference." ...