Preliminary data suggest that inactivated vaccine-induced neutralizing antibodies against SARS-CoV-2 decrease at six months after vaccination. Observational, unpublished data also indicate that vaccine effectiveness against Covid-19 wanes over time. Thus, the investigators aimed to determine the reactogenicity, safety, and immunogenicity of a homologous or heterologous booster of SARS-CoV-2 vaccines among people already immunized with an inactivated SARS-CoV-2 vaccine. The study focuses on the elderly population and healthcare workers.
Biological: Placebo
0.3 mL IM saline solution
Biological: Inactivated vaccine booster
0.5 mL IM
Other Name: CoronaVac
Biological: mRNA vaccine booster
0.3 mL IM
Other Name: BNT162b2
Drug: Viral vector vaccine booster
0.5 mL IM
Other Name: ChAdOx1
Inclusion Criteria:
- Full immunization with CoronaVac (2 doses; 0,28) prior to April 15, 2021
- Being a resident of any of the eligible Nursing Homes (located in the Metropolitan
Region of Chile)
- Healthcare workers of one of the eligible Nursing Homes.
- Healthcare workers of Hospital de Urgencia Asistencia Publica (HUAP, Santiago, Chile)
Exclusion Criteria:
- Prior history of Covid-19
- Not able to consent
ELEAMs (Nursing Homes)
Santiago, Chile
Hospital de Urgencia Asistencia Publica
Santiago, Chile