Center for Next-Generation Biologics Research,National Institute of Infectious Diseases, Japan Institute for Health Security, United States
Background/Case Studies: During the COVID-19 pandemic, over 90% of Japanese population received the SARS-CoV-2 mRNA vaccine, and blood donation is deferred 48 hours after mRNA vaccination in Japan. We have been monitored commercially available immunoglobulin products derived from Japanese and US plasma that contain extremely high titers of neutralizing antibodies, from both previously infected individuals and vaccine recipients. Krauson et al. reported that mRNA remained detectable in axillary lymph nodes of patients who developed myocarditis for up to 26 days, suggesting the possibility that mRNA may persist in the bloodstream. However, details regarding which components of the blood contained mRNA remained unclear.
Study
Design/Methods: Building on our previous work on booster vaccination efficacy and safety (Seki Y et al., Med. 2022), we collected fresh blood samples from the same healthcare worker cohort. From this group, 21 individuals who received the recently introduced JN.1-adapted Pfizer COMIRNATY mRNA vaccine in December 2024 were included in this analysis. Blood samples collected 10–14 days post-vaccination were separated into blood cell component and serum on the day of collection, and each was tested for mRNA presence. Recipients of Takeda's Nuvaxovid protein vaccine served as negative controls. We also tested IVIG/IMIG products manufactured from US and Japanese plasma for mRNA.
Results/Findings: mRNA was detected in both serum and blood clots from 20 out of 21 (95.2%) COMIRNATY recipients. The mRNA concentrations ranged from 17-120,000 cps/mL in serum and from 670-2,580,000 cps/mL in blood clots, with a clear correlation between serum and blood clot concentrations. Over 95% of mRNA was found in the serum. No correlation existed between mRNA concentrations and post-vaccination JN-1 neutralizing titer or the magnitude of titer increase from pre- to post-vaccination. No mRNA was detected in Nuvaxovid recipients or in IVIG/IMIG derived from either US or Japanese plasma, while these globulin products containing high neutralizing antibody titers.
Conclusions: mRNA was detectable in both blood clots and serum from individuals 10-14 days post-vaccination, when they would be eligible to donate blood. This suggests potential mRNA presence in various blood products including whole blood, fresh frozen plasma, platelets, and red blood cells. With 95% of mRNA found in serum, contamination risk is highest for plasma-containing products. Further research should examine residual mRNA functionality and investigate associations between mRNA persistence and adverse reactions.
