High SARS-CoV-2 Seroprevalence and Rapid Neutralizing Antibody Decline among Agricultural Workers in Rural Guatemala, June 2020-March 2021

Abstract

Essential agricultural workers work under occupational conditions that may increase the risk of SARS-CoV-2 exposure and transmission. Data from an agricultural worker cohort in Guatemala, and anti-SARS-CoV-2 nucleocapsid IgG (anti-N IgG) testing were used to estimate past infections and analyze risk factors associated with seropositivity at enrollment and association with SARS-CoV-2 infection. The stability of neutralizing antibody (NAb) responses were assessed in a subset of participants. The adjusted relative risk (aRR) for seroprevalence at enrollment was estimated accounting for correlations within worksites. At enrollment, 616 (46.2%) of 1334 (93.2%) participants had anti-N IgG results indicating prior SARS-CoV-2 infection. A cough ≤ 10 days prior to enrollment (aRR = 1.28, 95% CI: 1.13−1.46) and working as a packer (aRR = 2.00, 95% CI: 1.67−2.38) or packing manager within the plants (aRR = 1.82, 95% CI: 1.36−2.43) were associated with increased risk of seropositivity. COVID-19 incidence density among seronegative workers was 2.3/100 Person-Years (P-Y), higher than seropositive workers (0.4/100 P-Y). Most workers with follow-up NAb testing (65/77, 84%) exhibited a 95% average decrease in NAb titers in <6 months. While participants seropositive at baseline were less likely to experience a symptomatic SARS-CoV-2 infection during follow-up, NAb titers rapidly waned, underscoring the need for multipronged COVID-19 prevention strategies in the workplace, including vaccination.

Keywords: COVID-19; Guatemala; SARS-CoV-2; agricultural workers; cohort; seroprevalence.

Figure 1

Cumulative probability of symptomatic SARS-CoV-2 infection by anti-SARS-CoV-2. nucleocapsid IgG serostatus at enrollment. Anti-N IgG + = anti-SARS-CoV-2 nucleocapsid IgG positive, indicates a prior SARS-CoV-2 infection detected through antibody testing at enrollment (n = 616). Anti-N IgG − = anti-SARS-CoV-2 nucleocapsid IgG negative, no evidence of a prior SARS-CoV-2 infection at enrollment (n = 718).

Figure 2

Assessment of neutralizing antibody responses among individuals with serum specimens. Collected at two time points and subjected to a lentivirus-based pseudovirion assay. (A) Correlations between NAb IC50s assessed against nucleocapsid IgG positive COI values using linear regression. (B) Serum specimens with COI values <1 and >100 removed. (C) Mean NAb IC50 values for 4 groups of nucleocapsid IgG COI values evaluated using ANOVA followed by Kruskal-Wallis test and grouped based on whether the nucleocapsid IgG positive COI values were (D) decreasing, (E) vanishing, or (F) increasing. Trends are highlighted in the graphs on the left of each panel. For each group, the NAb IC50 titers are assessed (right graphs on each panel) and differences evaluated using a 2-tailed paired Student’s t-test. (G) The fold-decrease in NAb divided by the time interval between serum collection compared between specimens with various nucleocapsid IgG reactivity trends using ANOVA and Kruskal-Wallis test. For all panels: * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.