evidence: Cancer mRNA vaccines: clinical advances and future opportunities [...] Table 3 Clinical trials with mRNA vaccines against cancer [...] The requirement for safety in modern prophylactic vaccines is extremely stringent because the vaccines are administered to healthy individuals. Because the manufacturing process for mRNA does not require toxic chemicals or cell cultures that could be contaminated with adventitious viruses, mRNA production avoids the common risks associated with other vaccine platforms, including live virus, viral vectors, inactivated virus and subunit protein vaccines. Furthermore, the short manufacturing time for mRNA presents few opportunities to introduce contaminating microorganisms. In vaccinated people, the theoretical risks of infection or integration of the vector into host cell DNA are not a concern for mRNA. For the above reasons, mRNA vaccines have been considered a relatively safe vaccine format.