RESULTS Both mRNA vaccine sequences have been modified and are only ~70% identical to the spike reference genome on a nucleotide level, making them distinct from circulating infectious SARS-CoV-2 sequences. Of the 108 patient samples, 10 samples (9.3%) had partial or up to full sequences of the vaccine mRNA sequence DISCUSSION Analysis of mRNA vaccine function has focused on the immune response, and on protection of vaccinated individuals The LNPs have been reported to be rapidly cleared by immune cells, and mRNA rapidly degraded We expect that vaccine mRNA detected in plasma is contained within LNPs To our knowledge, our study is the first to detect Pfizer-BioNTech and Moderna COVID-19 mRNA vaccine sequences in blood after vaccination, and therefore provides new knowledge regarding the timeframe in which the mRNA can be detected. A future prospective study to establish the half-life of mRNA vaccines in vaccine recipients could be performed