A study released by UCLA researchers shows that antibodies against the virus that causes COVID-19 fall sharply during the first three months and decrease by roughly half every 36 days on average in people who have had mild cases of coronavirus.
Researchers believe the antibodies would disappear within roughly a year if sustained at that rate.
The study, published in the peer-reviewed New England Journal of Medicine, is the first to carefully estimate the rate at which the antibodies against SARS-CoV-2 disappear, according to researchers.
The study analyzed antibody test results from 20 women and 14 men ranging in age from 21 to 68, including four who hadn't been tested for COVID19 but had symptoms compatible with coronavirus and had cohabitated with people who were known to have the virus. Most had been mildly ill.
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Antibody tests were conducted of patients' blood samples at an average of 36 days and 82 days after their initial 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 comprise the majority of persons with COVID-19," researchers wrote in the article detailing the study.
Researchers noted that their findings "call for caution" about antibody-based "immunity passports" for people who have had COVID-19 to return to work or travel, along with the potential for "herd immunity" and possibly vaccine durability.
"Further studies will be needed to define a quantitative protection threshold and rate of decline of antiviral antibodies beyond 90 days," the researchers noted.