Introduction
RBD
ADENOVIRUS, SARS-COV-2 INFECTION
Edited by: Ritthideach Yorsaeng, Chulalongkorn University, ThailandReviewed by: Gagandeep Singh, Icahn School of Medicine at Mount Sinai, United States; Andre Bafica, Federal University of Santa Catarina, Brazil†These authors have contributed equally to this work and share first authorship‡These authors have contributed equally to this work and share senior authorshipMultiple factors, including vaccine platform and prior vaccinations, influence vaccine responses. We compared antibody responses to CoronaVac (Sinovac) and ChAdOx1-S (AstraZeneca-Oxford) vaccination in 874 healthcare workers in Brazil. As participants were randomised to BCG vaccination or placebo in the preceding 0-6 months as part of the BCG vaccination to reduce the impact of COVID-19 in healthcare workers (BRACE) trial, we also investigated the influence of recent BCG vaccination on antibody responses to these COVID-19 vaccines. Twenty-eight days after the second dose of each vaccine, ChAdOx1-S induced a stronger anti-spike IgG response than CoronaVac vaccination. Recent BCG vaccination did not impact IgG antibody responses to ChAdOx1-S or CoronaVac.SARS-CoV-2, the causative pathogen of COVID-19, spreads through the respiratory tract and contact, posing a significant challenge to the healthcare system due to the potential transmission To combat the COVID-19 pandemic, vaccines based on different platforms were developed in parallel. Initially, these included replication deficient adenovirus, mRNA and whole-inactivated virus-based vaccines, with protein sub-unit vaccines being available later in the pandemic. Prior to the COVID-19 pandemic, mRNA and adenovirus-based vaccines had limited use in human and animal models and therefore differences in immune responses to these, and vaccines based on more established platforms (e.g. whole-inactivated, protein subunit) are under investigation.Due to global demand and limited supply, access to vaccines was limited. Given the increased SARS-CoV-2 exposure in healthcare settings, healthcare workers (along with the elderly) were prioritized for access to COVID-19 vaccinations. In Brazil, the predominant COVID-19 vaccines used for primary vaccination have been ChAdOx1-S (AstraZeneca-Oxford, AZD1222), BNT162b2 (Pfizer-BioNTech), and CoronaVac (Sinovac). ChAdOx1-S, a replication deficient adenovirus-based vaccine, and BNT162b2, an mRNA-based vaccine, induce both humoral and T cell responses to the SARS-CoV-2 spike protein and receptor binding domain (RBD) (Several factors influence the magnitude and persistence of immune responses to COVID-19 vaccines including prior SARS-CoV-2 infection, age and sex (