(P-BC-61) Long-term Persistence of Vaccine-derived mRNA in the Blood of Individuals Who Received Multiple Doses of SARS-CoV-2 mRNA Vaccines (Pfizer, COMIRNATY Intramuscular Injection)

Background/Case Studies: The SARS-CoV-2 emerged in China in late 2019 and became a pandemic. A new modality of vaccine, mRNA vaccines, has been licensed, and vaccination have been conducted worldwide. mRNA vaccines induce neutralizing antibodies, but they also have a high rate of adverse reactions. Therefore, donor eligibility and deferral policies were discussed in several countries. Different countries have introduced different deferral periods at the beginning of the vaccination program. These periods range from 0 to 28 days. However, several cases have been reported that mRNA vaccine recipients with severe adverse reactions who had Spike antigen present in their blood for longer period. In addition, Krauson AJ et al. reported that mRNA remained detectable in the axillary lymph nodes of patients who developed myocarditis for 26 days (NPJ Vaccines 2023), suggesting that mRNA may persist in the blood and tissues.

Study

Design/Methods: We have previously investigated the efficacy and safety of the third booster vaccination in healthcare workers (Seki Y et al., Med. 2022). In this study, we first established a highly sensitive detection system for mRNA vaccines in blood and measured mRNA levels in the blood of participants who received 1-3 doses (1-2 weeks after vaccination).

Results/Findings: After 1-2 weeks after the first vaccination, mRNA was detected in 96% (26/27) of participants, 100% (75/75) after the second vaccination and 100% (21/21) after the third vaccination. When serum nucleic acid levels were measured after the second vaccination (N=75), the mRNA concentration ranged from 100 cp to 8.3 × 10⁵ cp/mL, with an average of 1.3 × 10⁵ cp/mL. In addition, when mRNA was measured in the serum three months after vaccination, approximately 7% continued to show detectable levels. However, all samples were negative six months after vaccination.
We next checked for the presence of mRNA in immunoglobulin products presumably made from blood donated during the mRNA vaccination. As a result, no mRNA was detected in any of the immunoglobulin products, leading to the assumption that there is no effect of mRNA vaccine on immunoglobulin products.

Conclusions: This study found that mRNA was detectable in the serum of all vaccinees two weeks after vaccination from 1st to 3rd vaccination, even after the blood donation deferral period.Approximately three months later, mRNA was still detectable in 7% of the vaccinated individuals. We are currently adding blood-derived mRNA to various cells to verify the presence of functional mRNA in the blood and to study the effects of such addition. We are also analyzing the biological significance of the blood-derived mRNA.