S.R., N.R., J.G., S.O.M., and B.P. unique and advantageous house of mRNA vaccines for controlling infectious disease outbreaks. Subject terms: RNA vaccines, SARS-CoV-2 Introduction In comparison to traditional vaccines, novel mRNA vaccines can be developed and produced for distribution in record time. This makes them suitable for rapidly controlling outbreaks as exhibited in the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic1C4. Furthermore, clinical trials have now shown the rapid protective efficacy of mRNA vaccines post primary immunizations5,6. For example, the USP7/USP47 inhibitor Pfizer mRNA vaccine clinical trial has exhibited clear divergence between placebo and vaccine recipients only 12 days after the first dose was administered5. Here, we sought to investigate how quickly mRNA vaccines induce protective humoral immunity in comparison to other vaccine modalities in mice. Specifically, we immunized C57BL/6 mice intradermally as well as intramuscularly with mRNA or DNA vaccines encoding SARS-CoV-2 full-length pre-fusion stabilized Spike protein7,8. The mRNA vaccine induced binding as well as neutralizing antibody titers as early as 5 days post immunization. To examine the effect of innate immune triggers, we evaluated the innate cytokine profiles of the two vaccines hours post immunization. Compared to the DNA vaccine, the mRNA vaccine induced a more robust production of IL-5, IL-6, and MCP-1. To determine whether the rapid immune kinetics would translate to other mRNA vaccines of different diseases and antigens, we evaluated the immune kinetics of an mRNA vaccine expressing HIV-1 envelope along with DNA, protein, and Rhesus Adenovirus 52 (RhAd52) vaccines of the same antigen. We were able to observe the rapid induction of antibodies 5 days post mRNA vaccine immunization. The rapid humoral immune kinetics is an advantageous property of the mRNA vaccines, which further supports their use in mitigating infectious disease outbreaks. Results Rapid induction of binding antibody titers post SARS-CoV-2 Spike mRNA vaccination in mice To determine the kinetics of humoral immune response, C57BL/6 mice were vaccinated intramuscularly (I.M.) or intradermally (I.D.) with mRNA vaccines expressing SARS-CoV-2 Spike at doses of 1 1?g or 4?g. Additional groups of mice were immunized I.M. with a previously investigated DNA vaccine8 at a dose of 50?g USP7/USP47 inhibitor or with PBS as a sham control. Spike-specific binding antibodies USP7/USP47 inhibitor were measured in serum by ELISA. Spike-specific binding antibody titers (median 179; range 72C532) were observed by day 5 following I.D. immunization with the 4?g dose of the USP7/USP47 inhibitor mRNA vaccine (Fig. ?(Fig.1).1). Antibody titers were also observed 5 days post I.M. immunization, although I.D. immunization resulted in higher titers at this early timepoint (test. Reporting summary Further information on research design is available in the Nature Research Reporting Summary linked CACNA1C to this article. Supplementary information REPORTING SUMMARY(1.5M, pdf) Acknowledgements We thank J. Ventura and L. Tostanoski for nice guidance and assistance. We acknowledge funding from the National Institute of Health (AI124377, AI128751, AI126603, CA260476), CureVac, and the Ragon Institute of MGH, MIT, and Harvard. We thank Acuitas Therapeutics for LNP formulations of mRNA vaccines. Author contributions M.S.G. and D.H.B. designed and planned experiments. S.R., N.R., J.G., S.O.M., and B.P. provided mRNA vaccines and input on the study design. M.S.G. performed mouse immunizations, bleeds, and ELISAs. M.S.G. and J.Y. conducted neutralization assays. X.L. and A.C.C performed cytokine assays. M.S.G. analyzed data, performed the statistical analysis, and wrote the manuscript. S.R., N.R., J.G., J.Y., S.O.M., B.P., and D.H.B edited and offered critical input to the manuscript. USP7/USP47 inhibitor All co-authors reviewed the manuscript. Data availability The authors can confirm that all relevant data are included in the paper. Competing interests S.R., N.R., J.G., S.O.M., and B.P. are employees and may.