Longitudinal SARS-CoV-2 seroprevalence among learners, parents, and teachers in a South African school community.

INTRODUCTION

Longitudinal assessments of SARS-CoV-2 seroprevalence among a triad of parents, teachers and children in low-middle income countries are scarce. CoKiDSS assessed changes in seroprevalence among asymptomatic primary school learners, their parents, and teachers in a semi-rural South African school setting.

METHODS

SARS-CoV-2 seroprevalence was estimated at baseline (May-August 2023) and follow-up (October 2023) using a point-of-care COVID-19 IgG/IgM test. Results were adjusted for test sensitivity and specificity. Between-group differences and within-participant serostatus changes were assessed using Fisher's exact test, and McNemar's test, respectively.

RESULTS

292 participants (203 learners, 71 parents, and 18 teachers) were included in this analysis. At baseline, overall (all group combined), SARS-CoV-2 IgG seroprevalence was 73% (unadjusted) and 78% (adjusted for test sensitivity). Seropositivity was higher among learners compared to parents (74% unadjusted to 77% adjusted vs. 66% unadjusted to 69% adjusted), with teachers showing the highest levels (94% unadjusted to 99% adjusted). Approximately 2.7% of learners were IgM seropositive, while about 25% of participants were IgG/IgM seronegative (24% of learners, 34% of parents, and 5.6% of teachers). At follow-up, overall SARS-CoV-2 IgG seroprevalence rose to 85% (unadjusted) to 95% (adjusted), with increases across all groups (learners: 96%, parents: 90%, teachers: 100%). A group-level longitudinal assessment showed there were significant increases in IgG seropositivity among learners (74-90%, p < 0.0001) and parents (66-85%, p = 0.015), while teachers remained consistently seropositive. The individual-level longitudinal assessment demonstrated that 69% of participants remained seropositive at follow-up, while 20% of those seronegative at baseline were seropositive at follow-up (p < 0.001).

DISCUSSION: Three years after the COVID-19 pandemic, despite no reported symptoms, and no vaccination campaigns, SARS-CoV-2 IgG seroprevalence increased over the 3-4-month follow-up period, particularly among unvaccinated learners, suggesting ongoing exposure and antibody persistence, although causal attribution cannot be established. Teachers maintained consistently high seroprevalence, likely reflecting sustained antibodies following prior infection or vaccination. Data suggest high levels of circulating virus and asymptomatic spread created endemicity in this environment. These findings should not guide vaccination policy but instead inform understanding of population-level seroprevalence.