Hybrid SARS-CoV-2 immunity among frontline workers in a high-tourism setting: A community-based serosurvey in...

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.