key: cord-0988914-1ivmwxhm
authors: Syed, Dr. Mohamed Ahmed; Alnuaimi, Dr. Ahmed Sameer; Abdulla AQotba, Dr. Hamda
title: SARS-CoV-2 seropositivity and subsequent infection risk: a prospective cohort study
date: 2022-02-15
journal: IJID Regions
DOI: 10.1016/j.ijregi.2022.02.005
sha: 4ceefd2fa30214e64ef35e6983b6ca7a4561b30c
doc_id: 988914
cord_uid: 1ivmwxhm

Objectives : This aim of the study was to examine the relationship between seropositivity and subsequent infection. Design : A cohort study design was employed. Methods : A stratified random sampling was undertaken to identify individuals aged 10 years and above registered with Qatar's largest primary healthcare provider. A questionnaire was administered, and blood samples were collected and analysed for immunoglobulin G antibodies against SARS-CoV2 at baseline. Participants were followed up until 31st March 2021 (34 weeks follow up period) for vaccination status and a positive PCR test for SARS-CoV2. Results : A total of 2,044 individuals participated in the study (97.2% of planned sample). Of these 185 (9 %) were found to be seropositive at baseline. 450 individuals were vaccinated during the follow up period – 246 with one dose and 204 with two doses. 86 (4.2 %) individuals had a positive PCR test during the follow up period – 80 (3.9 %) seronegative and 6 (0.3 %) seropositive (5 undiluted and 1 with a titre ≥ 1: 8). Conclusions : Overall, the findings suggest reinfections are uncommon. Antibody concentrations potentially influence the risk of subsequent infection. Therefore, it might not be necessary to subject seropositive individuals to vaccination and quarantine policies that apply to seronegative individuals.

A total of 2,044 individuals participated in the study (97.2% of planned sample). Of these 185 (9 %) were found to be seropositive at baseline. 450 individuals were vaccinated during the follow up period -246 with one dose and 204 with two doses. 86 (4.2 %) individuals had a positive PCR test during the follow up period -80 (3.9 %) seronegative and 6 (0.3 %) seropositive (5 undiluted and 1 with a titre ≥ 1: 8).

Overall, the findings suggest reinfections are uncommon. Antibody concentrations potentially influence the risk of subsequent infection. Therefore, it might not be necessary to subject seropositive individuals to vaccination and quarantine policies that apply to seronegative individuals.

As of the 28 th of September 2021, over 18 months since the first cases of Severe Acute Table 1 Key strengths of the study are the random selection of participants from PHCC registered population and long follow up duration. However, its limitation includes statistically nonsignificant results due to small number of subsequent infections in the cohort that was followed up. This limitation however is unlikely to impact the overall results of the study.

Overall, the findings suggest reinfections are uncommon. Antibody concentrations potentially influence the risk of subsequent infection. Therefore, it might not be necessary to subject seropositive individuals to vaccination and quarantine policies that apply to seronegative individuals.

All authors declare no conflict of interest. 

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