They say necessity is the mother of invention, and that is certainly turning out to be the case for two COVID-19 vaccines that have sped from research through animal testing to widespread clinical testing in record time—just one year after the SARS-CoV-2 virus was first detected in China and less than 11 months after Chinese authorities shared the genetic sequence of the novel coronavirus with the world.
The two vaccines—mRNA-1273, developed by Cambridge, MA-based Moderna; and BNT162b2, developed by Pfizer in partnership with German immunotherapy company Biopharmaceutical New Technologies (BioNTech)—are both based on mRNA technology, a relatively new alternative to conventional vaccines.
The mRNA (messenger RNA) method has never been used for human vaccines, but it has been used effectively in animal models of the influenza virus, the Zika virus, and rabies, and is being tested for use with some types of cancer.
An mRNA vaccine for COVID-19 is encoded with “instructions” for the body to make portions of the coronavirus’s spike protein, which it uses to attach to and attack cells. When the encoded mRNA is injected, the body of the vaccine recipient produces the spike protein, which allows the immune system to develop antibodies against it and mount a response. The body is then “trained” to fight the spike protein and is therefore able to recognize and fight the real virus when the vaccinated person is exposed to it.
BNT162b2 by Pfizer and BioNTech
Pfizer and BioNTech joined forces to begin developing their vaccine in March and started phase 3 clinical trials in July. By November they had delivered both doses of the vaccine (or a placebo) to more than 41,000 volunteers.
According to Pfizer and BioNTech, their COVID-19 vaccine is 95% effective in preventing infections across all age, race and ethnicity demographics and causes no serious safety concerns.
The most severe side effect was fatigue, experienced by just 3.8% of volunteers after receiving the second dose of the vaccine, and headache, which was experienced by 2%.
The FDA has asked Pfizer to track the volunteers for any problems or side effects for at least two months after the second shot, and Pfizer will continue to collect information on efficacy and safety for two years.
If all goes according to plan, the company says it will be able to produce 50 million vaccine doses before the end of the year and 1.3 billion doses in 2021.
mRNA-1273 by Moderna
Moderna completed its first clinical batch of its mRNA COVID-19 vaccine, developed in cooperation with researchers from the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center, in February, and started phase 3 trials in July with 30,000 volunteers in the United States.
In November, Moderna released efficacy data showing its vaccine provides 94.5% protection against COVID-19. Side effects after the second dose included fatigue, experienced by 9.7% of recipients, muscle pain (8.9%), joint pain (5.2%), headache (4.5%), pain (4.1%), and redness at the injection site (2%).
Moderna has said it could deliver 20 million doses of its vaccine by the end of the year and has partnered with Swiss drug company Lonza to manufacture 400 million doses annually.
The Differences
While both the mRNA-1273 and BNT162b2 vaccines use mRNA technology and require two doses, there are some differences between the two.
One of the major differences has nothing to do with the vaccines themselves, but instead how they were funded. The Moderna vaccine was developed as part of the U.S. government’s Operation Warp Speed, while the Pfizer vaccine was developed with private funding. Operation Warp Speed did pay Pfizer $1.9 billion for 100 billion doses of its vaccine candidate, and $1.5 billion to Moderna for the same amount.
Another key difference is in the temperature the vaccine requires in order to stay viable. Pfizer’s BNT162b2 vaccine must be stored at -70°C (-94°F) or lower, which could make transportation and storage difficult because those temperatures can’t be accommodated by conventional freezers. Pfizer plans to develop custom packaging that uses dry ice to keep temperatures low.
Moderna’s vaccine is expected to remain stable at standard refrigerator temperatures of 2° to 8°C (36° to 46°F) for 30 days, and in long-term storage at standard freezer temperatures of -20°C (-4°F) for 6 months. Once the Moderna vaccine is removed from the refrigerator, it can be kept at room temperature for up to 12 hours.
The degree of side effects is also different, with Moderna reporting both a wider variety of side effects and a higher occurrence among volunteers.
Both Moderna and Pfizer are continuing ongoing trials, collecting data and monitoring their vaccines for efficacy and safety. Both companies applied for and received EUA (emergency use authorization) from the FDA, which has allowed them to begin delivering doses of the vaccines to high-risk groups and start large-scale manufacturing with the intent of delivering millions more doses in the first half of 2021.
