Nearly 20 million people studied: does the COVID vaccine still hold up?

NCT ID NCT06199934

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

First seen Jun 26, 2026 · Last updated Jun 26, 2026

Summary

This study looked at data from nearly 20 million people in California and Louisiana to see how well different versions of Pfizer's COVID-19 vaccine prevented severe illness, hospitalization, and death. Instead of enrolling new volunteers, researchers used existing health records and vaccine registries. The goal was to understand the vaccine's real-world effectiveness over time.

What this could mean

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

Active substance: BNT162b2 (Pfizer-BioNTech COVID-19 vaccine)
What this could lead to: If successful, this study could confirm how well updated COVID-19 vaccines work in real-world settings, helping guide future vaccination strategies.
What could go wrong: This is an observational study using existing data, not a controlled trial, so results may be affected by unmeasured factors. It cannot prove cause and effect.

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 prevention target

As listed by the trial registrant

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

COVID-19 VACCINES SARS-COV-2

Contacts and locations

Locations

Pfizer Global Headquarters

New York, New York, 10001, United States

More trials for these conditions

Other studies related to the condition(s) this trial covers.