ABSTRACT
Global population immunity to SARS-CoV-2 is accumulating through heterogenous combinations of infection and vaccination. Vaccine distribution in low- and middle-income countries has been variable and reliant on diverse vaccine platforms. We studied B-cell immunity in Mexico, a middle-income country where five different vaccines have been deployed to populations with high SARS-CoV-2 incidence. Levels of antibodies that bound a stabilized prefusion spike trimer, neutralizing antibody titers and memory B-cell expansion correlated with each other across vaccine platforms. Nevertheless, the vaccines elicited variable levels of B-cell immunity, and the majority of recipients had undetectable neutralizing activity against the recently emergent omicron variant. SARS-CoV-2 infection, experienced prior to or after vaccination potentiated B-cell immune responses and enabled the generation of neutralizing activity against omicron and SARS-CoV for all vaccines in nearly all individuals. These findings suggest that broad population immunity to SARS-CoV-2 will eventually be achieved, but by heterogenous paths
Subject(s)
COVID-19ABSTRACT
Background: We performed a longitudinal SARS-CoV-2 seroepidemiologic study in healthcare personnel of the two largest tertiary referral hospitals in Mexico City. Methods: Participants answered a computer-assisted self-administered interview and donated blood samples for antibody testing every three weeks from October 2020 to June 2021. Findings: 290/883 participants had a positive result in any of the antibody tests, yielding an overall adjusted prevalence in the study period of 33·5%. 235 positive tests were identified at baseline (prevalent cases), the remaining 55 positive tests were incident cases. Prevalent cases showed associations with both occupational (institution 2 vs. 1: adjusted odds ratio [aOR]=2·24, 95% confidence interval [CI]: 1·54, 3·25; laboratory technician vs. medical doctor: aOR=4·38, 95% CI: 1·75, 10·93) and community risk (municipality of residence Xochimilco vs. Tlalpan: aOR=2·03, 95% CI: 1·09, 3·79). The incidence rate was 3·0 cases per 100 person-months. Incident cases were mainly associated with community-acquired risk, due to contact with suspect/confirmed COVID-19 cases (HR=2·45, 95% CI: 1·21, 5·00).Interpretation: We observed similar level of exposure to SARS-CoV-2 in healthcare workers of the two largest tertiary COVID-19 referral centers in Mexico City to the general population. Most variables associated with exposure in this setting pointed toward community rather than occupational risk.Funding: Consejo Nacional de Ciencia y Tecnología (CONACyT) (Fondo FORDECYT-PRONACES) and the Mexican Government (Programa Presupuestal P016; Anexo 13 del Decreto del Presupuesto de Egresos de la Federación).Declaration of Interest: None to declare. Ethical Approval: The study was reviewed and approved by the Institutional Review Boards of both participating institutions.