Which COVID-19 shot causes fewer side effects? new study compares novavax and pfizer

NCT ID NCT06633835

Completed Knowledge-focused Sponsor: Novavax Source: ClinicalTrials.gov ↗

First seen Jun 24, 2026 · Last updated Jun 27, 2026 · Updated 1 time

Summary

This completed study looked at how often healthcare workers and first responders experienced short-term side effects (like fever or sore arm) after getting either the updated Novavax or Pfizer COVID-19 vaccine. About 660 adults who had at least one prior COVID-19 shot took part. The goal was to see which vaccine caused fewer reactions in the first two days after vaccination.

What this could mean

Our plain-language read of the trial. This is informational only — not medical advice or a prediction.

Active substance: Novavax COVID-19 vaccine (protein subunit) and Pfizer mRNA COVID-19 vaccine
What this could lead to: If successful, this study could help people choose which COVID-19 vaccine might cause fewer short-term side effects.
What could go wrong: This is a completed observational comparison, not a test of whether the vaccines prevent disease. Results only cover the first two days after vaccination and may not apply to the general public.

This is an AI summary of the original study and may miss details. Read our disclaimer.

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Conditions

The condition(s) this trial relates to.

COVID-19 Vaccine-Preventable Diseases

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

COVID-19 SARS-COV-2 INFECTION VACCINE-PREVENTABLE DISEASES

Contacts and locations

Locations

University of Utah School of Medicine

Salt Lake City, Utah, 84108, United States

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