Hybrid SARS-CoV-2 immunity among frontline workers in a high-tourism setting: A community-based serosurvey in Ambergris Caye, Belize, June 2022

Tourism is central to Belize's economy, yet the influx of international travelers may contribute to infectious disease introduction and transmission among local workers, including SARS-CoV-2. In June 2022, we conducted a cross-sectional seroepidemiologic study among tourism and government workers in the tropical island tourism center of Ambergris Caye, Belize. The goal of this study was to determine SARS-CoV-2 antibody prevalence for both vaccination (anti-spike protein) and natural infection (anti-nucleocapsid protein), vaccine uptake, history of COVID-like symptoms, and risks for infection two years into the pandemic. Workers from 30 hotels and government agencies were enrolled. Participants completed questionnaires to capture demographics, medical history, COVID-19 exposures, and vaccination history. Serum samples were tested for SARS-CoV-2 anti-spike IgG (indicative of vaccination and/or infection) and anti-nucleocapsid IgG (infection only). Of 551 participants, 428 (78%) were tourism workers and 123 (22%) government employees. COVID-19 vaccine uptake was high (98%), and anti-spike IgG seroprevalence was 99%; only three vaccinated participants were seronegative. Anti-nucleocapsid prevalence was 81%, indicating a high prevalence of past natural infection. Based on multivariable analysis, nucleocapsid positivity was independently associated with having ≥5 people in household (aOR=2.08, p = 0.018), while receiving a COVID-19 booster was protective (aOR=0.57, p = 0.013). Among 282 participants reporting previous COVID-19 or COVID-19-like illness, 46% sought medical care and eight were hospitalized. High seroprevalence of both vaccine- and infection-induced antibodies was observed, highlighting the emergence of hybrid immunity among frontline workers. These findings underscore the importance of continued surveillance and targeted public health interventions in tourism-dependent settings.