Immunogenicity Evaluation of Omicron Variant-based Vaccine and a Trivalent Vaccine in Adults Against COVID-19 in Chile

Inclusion Criteria: * Adults, male or female, over 18 years of age; * Fully vaccinated against SARS-CoV-2 with two initial doses of CoronaVac® vaccine and that have received two booster doses of a different vaccine (heterologous group) or with CoronaVac® (homologous group) at least 5 months before enrollment; * Capable of understanding and signing the informed consent form; * Availability and commitment to comply with study procedures and in-person and remote appointments. Exclusion Criteria: * Symptomatic COVID-19 diagnosed 60 days before enrollment (confirmed COVID-19 by RT-PCR or antigen test, or by being in close contact with a confirmed case); * Pregnant women (confirmed by urine pack test) or women who plan to get pregnant within the first 3 months of the study; * Known allergies to the vaccine components; * Evidence of uncontrolled metabolic, neurologic#, cardiac, pulmonary, hepatic, or renal disease. Significant changes in medical treatment or hospitalizations due to worsening conditions in the last three months are indicators of uncontrolled disease or unsuccessful adherence to the treatment; * Alteration of the immune system (neoplasms, except basal cell cancer), congenital or acquired immunodeficiencies, and uncontrolled autoimmune diseases. Significant changes in medical treatment or hospitalizations due to worsening conditions in the last three months are indicators of uncontrolled disease; * Behavioral, psychiatric, or cognitive conditions# that, according to…