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. 2022 Mar 1;74(4):622-629.
doi: 10.1093/cid/ciab495.

Risk of Reinfection After Seroconversion to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Population-based Propensity-score Matched Cohort Study

Antonio Leidi  1 , Flora Koegler  1 , Roxane Dumont  2 , Richard Dubos  2 , María-Eugenia Zaballa  2 , Giovanni Piumatti  2   3 , Matteo Coen  1 , Amandine Berner  1 , Pauline Darbellay Farhoumand  1 , Pauline Vetter  4 , Nicolas Vuilleumier  5 , Laurent Kaiser  4 , Delphine Courvoisier  6 , Andrew S Azman  2   7 , Idris Guessous  2 , Silvia Stringhini  2 ; SEROCoV-POP study group
Collaborators, Affiliations

Risk of Reinfection After Seroconversion to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Population-based Propensity-score Matched Cohort Study

Antonio Leidi et al. Clin Infect Dis. .

Abstract

Background: Serological assays detecting anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies are being widely deployed in studies and clinical practice. However, the duration and effectiveness of the protection conferred by the immune response remains to be assessed in population-based samples. To estimate the incidence of newly acquired SARS-CoV-2 infections in seropositive individuals as compared to seronegative controls, we conducted a retrospective longitudinal matched study.

Methods: A seroprevalence survey including a representative sample of the population was conducted in Geneva, Switzerland, between April and June 2020, immediately after the first pandemic wave. Seropositive participants were matched one-to-two to seronegative controls, using a propensity-score including age, gender, immunodeficiency, body mass index (BMI), smoking status, and education level. Each individual was linked to a state-registry of SARS-CoV-2 infections. Our primary outcome was confirmed infections occurring from serological status assessment to the end of the second pandemic wave (January 2021).

Results: Among 8344 serosurvey participants, 498 seropositive individuals were selected and matched with 996 seronegative controls. After a mean follow-up of 35.6 (standard deviation [SD] 3.2) weeks, 7 out of 498 (1.4%) seropositive subjects had a positive SARS-CoV-2 test, of whom 5 (1.0%) were classified as reinfections. In contrast, the infection rate was higher in seronegative individuals (15.5%, 154/996) during a similar follow-up period (mean 34.7 [SD 3.2] weeks), corresponding to a 94% (95% confidence interval [CI]: 86%- 98%, P < .001) reduction in the hazard of having a positive SARS-CoV-2 test for seropositives.

Conclusions: Seroconversion after SARS-CoV-2 infection confers protection against reinfection lasting at least 8 months. These findings could help global health authorities establishing priority for vaccine allocation.

Keywords: COVID-19; SARS-CoV-2; antibody; protection; reinfection.

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