Persistence of SARS-Cov-2 Igg Antibody Response among South African Adults: A Prospective Cohort Study (preprint)

This study assesses the durability of severe acute respiratory coronavirus-2 (SARS-CoV-2) anti-nucleocapsid (anti-N) immunoglobulin G (IgG) after infection, and examines its association with established risk factors among South African healthcare workers (HCWs). Blood samples were obtained from 390 HCWs with diagnosis of coronavirus disease 2019 (COVID-19) for assay of the SARS-CoV-2 anti-N IgG at two time points (Phase 1 & 2) between November 2020 and February 2021. Out of 390 HCWs with COVID-19 diagnosis, 267 (68.5%) had detectable SARS-CoV-2 anti-N IgG antibodies at the end of phase I. These antibodies persisted for 4-5 and 6-7 months in 76.4% and 16.1%, respectively. In the multivariate logistic regression model analysis, black participants were more likely to sustain SARS-CoV-2 anti-N IgG for 4-5 months. However, participants who were HIV positive were less likely to sustain SARS-CoV-2 anti-N IgG antibodies for 4-5 months. In addition, individuals who were <45 years of age were more likely to sustain SARS-CoV-2 anti-N IgG for 6-7 months. Of the 202 HCWs selected for phase 2, 116 participants (57.4%) had persistent SARS-CoV-2 anti-N IgG for an extended mean period of 223 days (7.5 months). Findings support the longevity of vaccine responses against SARS CoV-2 in black Africans.

Cumulative incidence of SARS-CoV-2 and associated risk factors among healthcare workers in the Eastern Cape, South Africa (preprint)

Objectives: This study assesses the cumulative incidence of SARS-CoV-2 infection among healthcare workers (HCWs) during South Africas first wave and examines the associated demographic, health-related, and occupational risk factors for infection. Methods: Multi-stage cluster sampling was used in a cross-sectional study to recruit 1,309 HCWs from two academic hospitals in the Eastern Cape, South Africa over six weeks in November and December 2020. Prior test results for SARS-CoV-2 polymerase chain reaction (PCR) and participants characteristics were recorded while a blood sample was drawn for detection of IgG antibodies against SARS-CoV-2 nucleocapsid protein. The primary outcome measure was the SARS-CoV-2 cumulative incidence rate, defined as the combined total of positive results for either PCR or IgG antibodies, divided by the total sample. The secondary outcome was significant risk factors associated with infection. Results: Of the total participants included in the analysis (N=1295), the majority were female (81.5%), of black race (78.7%) and nurses (44.8%). A total of 390 (30.1%) HCWs had a positive SARS-CoV-2 PCR result and SARS-CoV-2 antibodies were detected in 488 (37.7%), yielding a cumulative incidence of 47.2% (n = 611). In the adjusted logistic regression model, being overweight (Adjusted odds ratio (AOR) = 2.15, 95% CI 1.44-3.20), obese (AOR = 1.37, 95% CI 1.02-1.85) and living with HIV (AOR = 1.78, 95% CI 1.38-2.08) were independently associated with SARS-CoV-2 infection. There was no significant difference in infection rates between high, medium and low COVID-19 exposure working environments. Conclusions: The high SARS-CoV-2 cumulative incidence in the cohort was surprising this early in the epidemic and probably related to exposure both in and outside the hospitals. To mitigate the impact of SARS-CoV-2 among HCWs, infection prevention and control (IPC) strategies should target community transmission in addition to screening for HIV and metabolic conditions.