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

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.