There are eight mRNA COVID-19 vaccine candidates currently in Phase II or Phase III clinical trials. These vaccines are faster to develop than traditional vaccine formulations, as they use only the genetic sequence of the virus. Leading COVID-19 mRNA vaccine candidates reported greater than 90% efficacy, which raises concerns if other candidates in earlier stages of development can match that of the frontrunners, says GlobalData, a leading data and analytics company.

Arcturus Therapeutics’ potential single-dose vaccine ARCT-021 is reported to have demonstrated both humoral and cellular immunity to the vaccine antigen, at relatively low dose level, but it remains to seen in future clinical trials whether the vaccine candidate can meet the high efficacy bar set by the frontrunners.

Keshalini Sabaratnam at GlobalData comments: “A single-dose vaccine with less stringent storage requirements that could be manufactured cost-effectively would be easier to distribute in low- and middle-income countries that cannot afford expensive vaccines and lack cold-chain services.”

Both Pfizer/BioNTech’s BNT-162b2 and Moderna’s mRNA-1273 are two- dose vaccines. They also have stringent cold storage and distribution requirements, as mRNA drugs are inherently less stable than DNA-based drugs.

Sabaratnam concludes, “Two-shot vaccines come with challenges, including the logistics to ensure everyone receives full immunization and additional costs around manufacturing, supply, and running two vaccination visits. Cold storage requirements add a level of complication to the logistics of distribution, as very cold storage equipment may be limited, and increased tracking is required.”