Among endemic coronaviruses, viral reinfection is not atypical within a 1-year period, according to data published in the Journal of Infectious Diseases.

Furthermore, study investigators found that the genetic basis of innate immune response, rather than immune memory acquired after infection, may be a greater determinant of infection severity.

The immune mechanisms of adaptive immunity to the pandemic coronavirus SARS-CoV-2 (coronavirus disease 2019) remain unknown. To provide a useful reference for understanding re-infection risk, the profiles of recurring infections with 4 endemic coronaviruses — HKU1, 229E, NL63, and OC43 — were investigated. Data from sampling conducted in New York City between fall 2016 and spring 2018 were used. Nasal swabs were collected, along with self-reports of respiratory symptoms from 191 participants who provided at least 6 separate pairs of nasopharyngeal samples.

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Throughout the course of the study, 86 participants tested positive at least once for any coronavirus infection; 12 participants tested positive multiple times for the same coronavirus. Median time between reinfection events was 37 weeks. In terms of reinfection probability, no significant difference was noted for the probability of either a single or recurring positive test for beta-coronaviruses OC43 and HKU1.

Investigators reported no significant association between repeat infections and symptom severity; however, there was a strong association between symptom severity family cluster.

Investigators noted that the methods for this analysis are based on the hypothesis that infection probabilities are “comparable among participants enrolled at different times in the study.” However, coronavirus infection is seasonal, and one study limitation is the relative magnitude across years of seasonal coronavirus epidemics. Investigators stressed that their “estimates of infection and re-infection probabilities must be considered as a lower bound, due to the occurrence of weekly swabs missed by the participants and due to the design of the study itself, which may have missed infections of short duration in between consecutive weekly tests.”

Self-reporting of symptoms is another important limitation, as well as parents reporting symptoms for dependents introducing some bias. Finally, the high sensitivity of PCR tests meant small amounts of viral genetic material may be amplified but are not ascribable to active infections. The occurrence of repeated infections separated by 38 weeks was corroborated by repeating the analysis with different positivity thresholds. However, without virus sequencing, investigators cannot exclude the possibility that subsequent positives are the resurgence of the same infection rather than a new one.

“This study confirms that reinfections with the same coronavirus type occur in a time window shorter than 1 year, and finds no significant association between repeat infections and symptom severity,” the researchers concluded. Investigators recommend further analyses involving viral sequencing and serological testing in order to confirm repeated infections and disentangle the effects of antigenic drift and antibody waning. They also suggest studies analyzing the genetic basis of individual response to coronavirus infections.

Disclosure: One study author declared affiliations with industry. Please see the original reference for a full list of authors’ disclosures.


Galanti M, Shaman J. Direct observation of repeated infections with endemic coronaviruses [published online July 7, 2020]. J Infect Dis. doi:10.1093/infdis/jiaa392