Sanna De Jong, a nursing assistant, tested positive for COVID-19 on April 17 and suffered mild symptoms for 2 weeks. On May 2, she tested negative, but her symptoms re-emerged a few weeks later and she received a positive test for COVID-19 on July 3. De Jong is not the only case of a COVID-19 re-infection. The first suspected reinfection occurred in April, and since then at least 24 cases of reinfections have been officially confirmed in Korea, though this is “definitely an underestimate,” according to scientists.
To count as reinfection, a patient must have a positive PCR test twice with at least one symptom-free month in between. However, the second test may also be positive because the patient could still have “residues of nonreplicating viral RNA from their original infection in the respiratory tract because of an infection with two viruses at the same time or because they had suppressed but never fully cleared the virus.” As such, reinfection must be confirmed by identifying two full virus sequences from the first and second illnesses that are sufficiently different. However, in many cases “the genetic material just isn’t there” according to Paul Moss at the University of Birmingham. Further, many labs don’t have the time or money to do so. As such, the “number of genetically proven reinfections is orders of magnitude lower than that of suspected reinfections.”
Although antibodies can wane within months, particularly in patients with less severe disease, they sometimes persist. Neutralizing antibodies as well as memory B cells and T cells also seem to be stable over at least 6 months which should “prevent most people from getting hospitalized disease or severe disease for many years.” People who have serious COVID-19 mount the strongest responses, just as is the case for the two other serious human diseases caused by coronavirus: SARS and MERS. Both SARS and MERS trigger high antibody levels that last up to 2 years, and T cell responses to SARS can be detected even longer.
- Claire Hillier, Nov. 20
Reference:
Jop de Vrieze et al. “More People Are Getting COVID-19 Twice, Suggesting Immunity Wanes Quickly in Some.” Science, 18 Nov. 2020, www.sciencemag.org/news/2020/11/more-people-are-getting-covid-19-twice-suggesting-immunity-wanes-quickly-some.
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