Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine

Nat Med. 2021 May;27(5):790-792. doi: 10.1038/s41591-021-01316-7. Epub 2021 Mar 29.


Beyond their substantial protection of individual vaccinees, coronavirus disease 2019 (COVID-19) vaccines might reduce viral load in breakthrough infection and thereby further suppress onward transmission. In this analysis of a real-world dataset of positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test results after inoculation with the BNT162b2 messenger RNA vaccine, we found that the viral load was substantially reduced for infections occurring 12-37 d after the first dose of vaccine. These reduced viral loads hint at a potentially lower infectiousness, further contributing to vaccine effect on virus spread.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • BNT162 Vaccine
  • COVID-19 / prevention & control*
  • COVID-19 / virology
  • COVID-19 Vaccines / immunology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • SARS-CoV-2 / immunology*
  • SARS-CoV-2 / isolation & purification
  • Vaccination*
  • Viral Load*
  • Young Adult


  • COVID-19 Vaccines
  • BNT162 Vaccine