Can a smaller booster dose still protect against COVID-19?

NCT ID NCT05265065

First seen Jun 27, 2026 · Last updated Jun 27, 2026

Summary

This study looked at whether a smaller (fractional) dose of the Pfizer-BioNTech COVID-19 booster works as well as the standard dose. It involved 601 healthy adults in Mongolia who had already received two doses of Sinopharm, AstraZeneca, or Sputnik vaccines 6 to 9 months earlier. The goal was to measure immune response and side effects after the booster.

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Conditions

The condition(s) this trial relates to.

COVID-19

As listed by the trial registrant

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

Contacts and locations

Locations

  • District Health Centre

    Ulaanbaatar, Mongolia