Vaccines (Jun 2022)

Immunization and SARS-CoV-2 Antibody Seroprevalence in a Country with High Vaccination Coverage: Lessons from Chile

  • Ximena Aguilera,
  • Claudia González,
  • Mauricio Apablaza,
  • Paola Rubilar,
  • Gloria Icaza,
  • Muriel Ramírez-Santana,
  • Claudia Pérez,
  • Lina Jimena Cortes,
  • Loreto Núñez-Franz,
  • Rubén Quezada-Gaete,
  • Carla Castillo-Laborde,
  • Juan Correa,
  • Macarena Said,
  • Juan Hormazábal,
  • Cecilia Vial,
  • Pablo Vial

DOI
https://doi.org/10.3390/vaccines10071002
Journal volume & issue
Vol. 10, no. 7
p. 1002

Abstract

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Chile is among the most successful nations worldwide in terms of its COVID-19 vaccine rollout. By 31 December 2021, 84.1% of the population was fully vaccinated, and 56.1% received booster doses using different COVID-19 vaccines. In this context, we aimed to estimate the prevalence of anti-SARS-CoV-2 antibodies following the infection and vaccination campaign. Using a three-stage stratified sampling, we performed a population-based cross-sectional serosurvey based on a representative sample of three Chilean cities. Selected participants were blood-sampled on-site and answered a short COVID-19 and vaccination history questionnaire using Wantai SARS-CoV-2 Ab ELISA to determine seroprevalence. We recruited 2198 individuals aged 7–93 between 5 October and 25 November 2021; 2132 individuals received COVID-19 vaccinations (97%), 67 (3.1%) received one dose, 2065 (93.9%) received two doses, and 936 received the booster jab (42.6%). Antibody seroprevalence reached 97.3%, ranging from 40.9% among those not vaccinated to 99.8% in those with booster doses (OR = 674.6, 154.8–2938.5). SARS-CoV-2 antibodies were associated with vaccination, previous COVID-19 diagnosis, age group, and city of residence. In contrast, we found no significant differences in the type of vaccine used, education, nationality, or type of health insurance. We found a seroprevalence close to 100%, primarily due to the successful vaccination program, which strongly emphasizes universal access.

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