# The Safety of Administering a Second Dose of a COVID-19 mRNA Vaccine in Individuals Who Experienced a Systemic Allergic Reaction to an Initial Dose

> **NCT04977479** · PHASE2 · COMPLETED · sponsor: **National Institute of Allergy and Infectious Diseases (NIAID)** · enrollment: 20 (actual)

## Conditions studied

- Systemic Allergic Reaction

## Interventions

- **BIOLOGICAL:** Pfizer-BioNTech COVID-19 Vaccine (Comirnaty)
- **OTHER:** Placebo
- **BIOLOGICAL:** Pfizer-BioNTech COVID-19 Vaccine, Bivalent

## Key facts

- **NCT ID:** NCT04977479
- **Lead sponsor:** National Institute of Allergy and Infectious Diseases (NIAID)
- **Sponsor class:** NIH
- **Phase:** PHASE2
- **Study type:** INTERVENTIONAL
- **Status:** COMPLETED
- **Start date:** 2021-09-08
- **Primary completion:** 2022-06-17
- **Final completion:** 2023-02-22
- **Target enrollment:** 20 (ACTUAL)
- **Last updated:** 2023-10-16


## Primary source

ClinicalTrials.gov registry: https://clinicaltrials.gov/study/NCT04977479

## Citation

> US National Library of Medicine, ClinicalTrials.gov registration NCT04977479, "The Safety of Administering a Second Dose of a COVID-19 mRNA Vaccine in Individuals Who Experienced a Systemic Allergic Reaction to an Initial Dose". Retrieved via AI Analytics 2026-06-25 from https://api.ai-analytics.org/clinical/NCT04977479. Licensed CC0.

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