# Delayed Heterologous SARS-CoV-2 Vaccine Dosing (Boost) After Receipt of EUA Vaccines

> **NCT04889209** · PHASE1,PHASE2 · COMPLETED · sponsor: **National Institute of Allergy and Infectious Diseases (NIAID)** · enrollment: 867 (actual)

## Conditions studied

- COVID-19

## Interventions

- **BIOLOGICAL:** Ad26.COV2.S
- **BIOLOGICAL:** BNT162b2
- **BIOLOGICAL:** mRNA-1273
- **BIOLOGICAL:** mRNA-1273.211
- **BIOLOGICAL:** mRNA-1273.222
- **BIOLOGICAL:** SARS-CoV-2 rS/M1

## Key facts

- **NCT ID:** NCT04889209
- **Lead sponsor:** National Institute of Allergy and Infectious Diseases (NIAID)
- **Sponsor class:** NIH
- **Phase:** PHASE1,PHASE2
- **Study type:** INTERVENTIONAL
- **Status:** COMPLETED
- **Start date:** 2021-05-28
- **Primary completion:** 2023-06-16
- **Final completion:** 2023-06-16
- **Target enrollment:** 867 (ACTUAL)
- **Last updated:** 2025-04-20


## Primary source

ClinicalTrials.gov registry: https://clinicaltrials.gov/study/NCT04889209

## Citation

> US National Library of Medicine, ClinicalTrials.gov registration NCT04889209, "Delayed Heterologous SARS-CoV-2 Vaccine Dosing (Boost) After Receipt of EUA Vaccines". Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/clinical/NCT04889209. Licensed CC0.

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