6.3 mRNA vaccines
As a result of tremendous advancement in biotechnology, mRNA vaccines
represent a significant upgrade over conventional vaccine strategies
owing to their higher potency, short production cycles, low-cost
manufacturing, and safe administration (Pardi et al., 2018). The
sequential events in the process of mRNA vaccine development constitutes
antigen selection, sequence analysis and optimization, screening of
modified nucleotides, selection of delivery system, immune response and
safety evaluation tests (Jahanafrooz et al., 2020). A potential
advantage of mRNA vaccines is the convenient availability of a portable
mRNA ’printing’ facility for the production of mRNA is large quantities
(Saif, 2020). The use of nanotechnology enhances the delivery of mRNA
vaccine via intramuscular or intradermal route by using lipid
nanoparticle coating (Rauch et al., 2018; Saif, 2020). Thus, a number of
major biotech companies have ventured into COVID-19 vaccine development
using the advanced nucleic acid vaccine platforms, such Moderna and
CureVac (Chen et al., 2020). Since, no mRNA vaccine has been licenced
till date its quality and safety testing may take more than the expected
time (Zhang et al., 2020). However, with advancement in nucleic acid
technologies the nucleic acid vaccine performance in humans has improved
due to new modifications and formulations and this approach is expected
to ensure the first licenced human nucleic acid vaccine very soon (Chen
et al., 2020). In the race of mRNA vaccine development SARS-CoV-2 mRNA
vaccine (mRNA-1273) developed by Moderna is the most talked about. It is
a lipid nanoparticle- encapsulated mRNA vaccine encoding for S protein.
Its manufacturing cost is supported by the Coalition of the Epidemic
Preparedness Innovations. This vaccine is currently in phase I
open-label dose-ranging trial in humans at Kaiser Permanente Washington
Health Research Institute in Seattle and phase II trial to assess the
safety, reactogenicity, and immunogenicity is expected in June month of
this year (Moderna, 2020). Further, the triangular collaboration between
Fudan University, Shanghai Jiaotong University, and Bluebird
Biopharmaceutical Company has come up with two different strategies for
the development of SARS-CoV-2 mRNA vaccine. The first one targets S
protein and RBD of S1 of SARS-CoV-2 and second one uses mRNA to express
virus-like particles in vivo (Zhang et al., 2020). The other notable
companies and institutions who ventured into SARS-CoV-2 mRNA vaccine
development and are in different stages of development are CureVac AG,
Stermirna Therapeutics, BDGENE Therapeutics, Guanhao Biotech, ZY
Therapeutics Inc., CanSino Biologics Inc., Baylor College of Medicine,
University of Texas, etc.