Reactogenicity, Safety, and Immunogenicity of Covid-19 Vaccine Booster

Reactogenicidad, Seguridad e Inmunogenicidad de Dosis de Refuerzo de Vacunas Contra SARS-CoV-2 en Chile (Estudio REFUERZO)

Status

UNKNOWN

Phases

Phase 2

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT04992182

Acronym

REFUERZO

Enrollment

534

Registered

2021-08-05

Start date

2021-07-08

Completion date

2022-06-30

Last updated

2021-08-05

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Covid19

Keywords

covid-19, inactivated vaccine, booster, Chile

Brief summary

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 Observational, unpublished data also indicate that vaccine effectiveness against Covid-19 wanes over time.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.

Interventions

BIOLOGICALPlacebo

0.3 mL IM saline solution

BIOLOGICALInactivated vaccine booster

0.5 mL IM

BIOLOGICALmRNA vaccine booster

0.3 mL IM

DRUGViral vector vaccine booster

0.5 mL IM

Study design

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

TREATMENT

Masking

DOUBLE (Subject, Investigator)

Eligibility

Sex/Gender

ALL

Age

18 Years to No maximum

Healthy volunteers

Yes

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

Design outcomes

Primary

Measure	Time frame	Description
Early humoral response	Baseline (90-120 days after second dose of CoronaVac) and 15 days post booster dose	Change in SARS-CoV-2 neutralizing antibody levels
Immunogenicity	Baseline, 15, 30, 60, and 90 days post booster dose	Change in SARS-CoV-2 neutralizing antibody levels

Secondary

Measure	Time frame	Description
Reactogenicity	days 7, 28, and 3 months post booster dose	Solicited and unsolicited. Events will be assessed by scheduled visits performed by nursing home´s nurse stuff. Telephone numbers, including the PI´s cell phone will be available 24/7 for reporting any unsolicited reaction. Reporting will follow national regulations available at the Institute of Public Health web page (https://www.ispch.cl/anamed/farmacovigilancia/vacunas/como-notificar-esavi/)
Safety of booster dose	In addition to the scheduled visits mentioned in Outcome 3, Telephone numbers, including the PI´s cell phone will be available 24/7 throughout the study (1 year) for reporting any unsolicited reaction.	Number of subjects presenting serious adverse events post booster dose.

Countries

Chile

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 12, 2026