September 2, 2020

COVID-19 antibodies good for at least 4 months

A new study has provided some answers about COVID-19 antibodies—but also raises new questions. The Iceland study found that antibodies persisted in some people for at least four months after they contracted the coronavirus, per the study published today in the New England Journal of Medicine.

Researchers arrived at that conclusion by looking for antibodies in blood samples taken from 30,576 people in Iceland and then zeroing in on 487 people who took more than one antibody test.

Those tests showed that the level of antibodies rose during months one and two and then plateaued in months three and four. "There is no evidence of any slight decrease," says study co-author Dr. Kari Stefansson.

Antibody levels were higher in men versus women ("who tend to become less sick than men," per the study), among nonsmokers versus smokers, and in older patients. Of note: Of the blood samples that came from people who tested positive for COVID, the study found not all of them showed the presence of antibodies.

The researchers speculate that those diagnoses were false positives, or that those with weaker immune responses just might not develop antibodies.

And then there's the even bigger question: Do those antibodies actually protect a person against reinfection? An accompanying editorial notes that the study's focus on a "homogeneous population" means further research is needed, but "this study provides hope that host immunity to this unpredictable and highly contagious virus may not be fleeting and may be similar to that elicited by most other viral infections."