Coronavirus Antibodies Drop Precipitously 3 Months After Mild Cases

UCLA researchers found that the antibodies against SARS-CoV-2 decreased by half every 73 days.

The prevalence of antibodies for people recovering from a mild case of COVID-19 dropped precipitously after less than three months, according to a research letter published this week in The New England Journal of Medicine.

UCLA researchers wrote that a small study of 34 patients, with a median age of 43, found that the antibodies against SARS-CoV-2 — the virus that causes the disease — decreased by roughly half every 73 days, and would likely disappear entirely within a year at such a rate.

The findings could have implications for the long-term effect of potential vaccines and could also affect the ongoing debate in the public health and policy arenas about the merits of "herd immunity."  

The study followed 20 women and 14 men who recovered from mild cases of COVID-19. Antibody tests were taken 36 days and 82 days after the symptoms of infection.

"Our findings raise concern that humoral immunity against SARS-CoV-2 may not be long lasting in persons with mild illness, who compose the majority of persons with Covid-19," the researchers wrote.

"It is difficult to extrapolate beyond our observation period of approximately 90 days because it is likely that the decay will decelerate," they wrote.

"Still, the results call for caution regarding antibody-based 'immunity passports,' herd immunity, and perhaps vaccine durability, especially in light of short-lived immunity against common human coronaviruses."