mRNA (messenger RNA), transcribed from a chain of genetic material DNA, is a chain structure molecule containing four bases (A, U, G, and C). If the mRNA encoding the S protein of the virus is injected into the human body, human cells can directly express the antigen protein, thus stimulating immune response.

mRNA is a single-stranded macromolecule, which is extremely fragile and unstable in vivo. Extracellular membrane barrier, intracellular enzyme degradation, and intracellular immune response are the three barriers blocking mRNA as an exogenous macromolecule. But this problem has been solved by the revolutionary lipid nanoparticle (LNP) delivery technology that can not only protect mRNA molecules, but also help mRNA molecules guide cells to translate viral proteins and neutralize viruses.

At present, two mRNA vaccines against COVID-19 have been approved by the FDA already.

  1. Comirnaty

On August 23, 2021, the FDA officially approved Comirnaty against COVID-19, jointly developed by Pfizer and a German biotechnology company BioNTech, to be used in people aged 16 and over to prevent SARS-CoV-2 infection.

Comirnaty is the world’s first COVID-19 vaccine officially approved based on complete phase III clinical trial data. Since it was authorized for emergency use in the United States on December 11, 2020 to be officially approved, Pfizer/BioNTech has provided more than 1.2 billion doses of the COVID-19 vaccine to more than 120 countries or regions around the world.

In the critical clinical phase III study, an analysis of 927 confirmed symptomatic COVID-19 cases showed that Comirnaty was effective in preventing COVID-19 between 7 days and 6 months after the second dose vaccination. According to the definition of the US Centers for Disease Control and Prevention (CDC), the effective rate of Comirnaty for the prevention of severe COVID-19 disease is 100%. According to the FDA, the effectiveness for the prevention of severe COVID-19 diseases is 95.3%. The safety data were collected from more than 12,000 vaccinators who had been followed up for at least 6 months after the second dose of the vaccine, indicating that Comirnaty was safe and well-tolerated.

  1. Spikevax

On January 31, 2022, Moderna’s COVID-19 vaccine Spikevax was approved to prevent people over the age of 18 from SARS-CoV-2 infection, the second mRNA COVID-19 vaccine officially approved by the FDA, which had previously received for emergency use authorization (EUA) on December 18, 2020 based on FDA’s evaluation and analysis of ongoing randomized, blind, and placebo-controlled clinical trials, and real-world data after EUA to further test the safety and effectiveness of the vaccine.

Spikevax validity data were accumulated before the emergence of Omicron variant, and the data analysis included 14,287 vaccinators and 14,164 placebo vaccinators over the age of 18 and were not infected with SARS-CoV-2 before the first vaccination. Data analysis shows that the effective rate of Spikevax in preventing symptomatic COVID-19 is 93.2%, and the effective rate of people aged 18-65 is 93.4%. The effective rate of people over 65 years old is 91.5%. There were 55 cases of COVID-19 in the vaccine group and 744 cases of COVID-19 in the placebo group. The effective rate of the vaccine in preventing serious diseases reached 98.2%. In addition, the main side effects of the vaccine include injection site reaction, joint pain, vomiting, fatigue, headache, muscle pain, chills, injection site swelling, and fever. 

Comparison of two mRNA Vaccines
Category Pfizer/BioNTech Moderna
Trade Name Comirnaty Spikevax
Specifications 0.3mL 0.5mL
Effective Ingredients BNT-162b2 30μg mRNA-1273 100μg
Lonizable Phospholipid ALC-3015 430μg SM-102 1930μg
Cholesterol 200μg
DSPC 90μg
PEG Phospholipid ALC-0159 50μg PEG2000-DMG
Buffer Salt Potassium Chloride 100μg Trihydroxymethyl Methylamine 310μg
Potassium Dihydrogen Phosphate 100μg Bradyloxylamine Hydrochloride 1108μg
Sodium Chloride 360μg Acetic Acid 43μg
Sodium Monohydrogen Phosphate Dihydrate 70μg Sodium acetate Trihydrate 200μg
Sucrose 6mg Sucrose 43.5mg