Sub-cutaneous Pfizer/BioNTech COVID-19 vaccine administration results in seroconversion among young adults

Vaccine. 2021 Oct 8;39(42):6210-6212. doi: 10.1016/j.vaccine.2021.07.096. Epub 2021 Aug 5.


Route of vaccine administration plays a role in extent and quality of immunogenicity. 790 military personnel accidentally received the first of two doses of Pfizer/BioNTech mRNA anti Covid-19 vaccine using a needle intended for subcutaneous administration. A serological blood test (on day 21, prior to the second intramuscular dose) was performed, analyzing whether immunological response was elicited. 98.2% demonstrated seroconversion. IgG titers were negatively correlated with age and did not correlate with BMI. Our results could help reassure providers confronted with a similar mistake and may even imply a possibly new and effective administration route.

Keywords: BNT162b2; COVID 19; SARS-CoV-2; Seroconversion; mRNA vaccine.

MeSH terms

  • COVID-19 Vaccines*
  • COVID-19*
  • Humans
  • SARS-CoV-2
  • Seroconversion
  • Young Adult


  • COVID-19 Vaccines