Vaccine mRNA Can Be Detected in Blood at 15 Days Post-Vaccination

COVID-19 mRNA vaccines effectively reduce incidence of severe disease, hospitalisation and death. The biodistribution and pharmacokinetics of the mRNA-containing lipid nanoparticles (LNPs) in these vaccines are unknown in humans. In this study, we used qPCR to track circulating mRNA in blood at different time-points after BNT162b2 vaccination in a small cohort of healthy individuals. We found that vaccine-associated synthetic mRNA persists in systemic circulation for at least 2 weeks. Furthermore, we used transmission electron microscopy (TEM) to investigate SARS-CoV-2 spike protein expression in human leukemic cells and in primary mononuclear blood cells treated in vitro with the BNT162b2 vaccine. TEM revealed morphological changes suggestive of LNP uptake, but only a small fraction of K562 leukemic cells presented spike-like structures at the cell surface, suggesting reduced levels of expression for these specific phenotypes.

Automated summary

COVID-19 mRNA vaccines effectively reduce the incidence of severe disease, hospitalization, and death. This study used qPCR to track synthetic mRNA in the blood after BNT162b2 vaccination and found that the mRNA persists in the systemic circulation for at least 2 weeks. Transmission electron microscopy revealed morphological changes indicative of lipid nanoparticle uptake, but only a small fraction of leukemic cells showed spike-like structures on the cell surface, suggesting reduced expression levels for these specific phenotypes.