NCT05343871

Immunogenicity and Safety of Fractional Booster Dose of COVID-19 Vaccines Available for Use in Pakistan/Brazil: A Phase 4 Dose-optimizing Trial

Randomized Controlled Trial to Assess the Immunogenicity and Safety of Full Versus Fractional Dose of Pfizer/BioNTech, AstraZeneca, and Sinovac COVID-19 Vaccines Given as a Booster Dose at Least 6 Months After Primary Vaccination Series or PCR-confirmed Infection With SARS-CoV-2 in Healthy Adults

• Status: Completed
• Phase: Phase 4
• Study type: Interventional
• Enrollment: 2,354 (actual)
• Sponsor: Albert B. Sabin Vaccine Institute · Academic / Other
• Sex: All
• Age: 18 Years – 60 Years
• Healthy volunteers: Accepted

Summary

Since the emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogen in late 2019, millions of people around the world have fallen ill and died from coronavirus disease 2019 (COVID-19), with variant-fueled case spikes causing repeated cycles of morbidity and mortality. The rapid development and emergency use authorization of vaccines against SARS-CoV-2 presents an enormous opportunity to protect populations, but bottlenecks in production have led to demand for vaccines that far outpaces supply. This project will investigate the immunogenicity of fractional doses of SARS-CoV-2 vaccines given a minimum of six months following an initial two-dose schedule or following natural immunity via documented infection. The consortium of research partners from the Sabin Vaccine Institute, Aga Khan University, Fundação Oswaldo Cruz (Fiocruz), and Stanford University will recruit volunteers to receive a full or fractional booster dose of BNT162b2, AZD1222 or Sinovac following receipt of their primary vaccination series or PCR-confirmed natural infection in Pakistan. The research team will follow participants for six months from boosting, with blood draws at baseline, 28 days, 3 months and 6 months, and measure sero-response rate (SRR) by anti-Spike immunoglobulin G (IgG) binding enzyme-linked immunosorbent assay (ELISA) with the ultimate aim of identifying whether fractional doses provide a similar immune response compared to full doses of vaccine.

Conditions

• COVID-19

Interventions

Type	Name	Description
BIOLOGICAL	Sinovac	Sinovac inactivated COVID-19 vaccine: ● Full dose (0.5 ml)
BIOLOGICAL	AZD1222	AstraZeneca ChAdOx1-S recombinant AZD1222 vaccine: * Full dose (0.5 ml) * Half dose (0.25 ml)
BIOLOGICAL	BNT162b2	Pfizer/BioNTech BNT162b2 mRNA vaccine: * Full dose (30 micrograms) * Half dose (15 micrograms) * One-third dose (10 micrograms)

Timeline

• Start date: 2022-07-05
• Primary completion: 2023-07-28
• Completion: 2024-01-11
• First posted: 2022-04-25
• Last updated: 2024-01-30

Locations

2 sites across 2 countries: Brazil, Pakistan