A second COVID-19 vaccine now also appears highly effective in preventing illness following exposure to the virus that causes the disease.
The biotech company Moderna Inc. said Monday that its experimental vaccine was 94.5% effective in preventing disease, according to an analysis of its clinical trial.
The news comes a week after Pfizer and BioNTech said their vaccine was more than 90% effective.
The results for both vaccines come from interim analyses of large clinical studies. In the Moderna study there were 30,000 volunteers. Half got two doses of the vaccine 28 days apart; half got two shots of a placebo on the same schedule.
There were 95 instances of COVID-19 illness among the study participants; only five of those cases were in the vaccinated group. Ninety were in the group receiving the placebo. Of these, there were 11 cases of severe disease. The results indicate the vaccine was inducing the kind of immune response that protects people if they were exposed to the coronavirus.
"This positive interim analysis from our Phase 3 study has given us the first clinical validation that our vaccine can prevent COVID-19 disease, including severe disease," Stéphane Bancel, chief executive officer of Moderna, said in a statement.
Both the Moderna and Pfizer vaccines use the same technology to make their vaccines. It's based on a molecule known as mRNA, or messenger RNA. That molecule contains genetic instructions for making proteins inside cells.
For the vaccine, researchers created an mRNA with the code for making the coronavirus spike protein. The protein is the key to the virus infecting cells. It's also what can trigger someone's immune system to make antibodies against the virus, but without causing infection since the rest of the virus is missing.
That two mRNA vaccines appear to be working is remarkable, since the technology is new and there hasn't been an mRNA vaccine approved by the Food and Drug Administration made to date.
The Moderna and Pfizer studies were conducted using slightly different protocols. To be counted as a COVID-19 case, participants in the Moderna study had to have at least two symptoms of disease in addition to a positive test for the virus. The Pfizer study required only one symptom. Also, Moderna waited 14 days following the second injection to begin counting cases; Pfizer's study started counting at seven days.
The vaccines also differ in their storage requirements. Moderna says its vaccine can be safely stored in freezers at about 25 degrees Fahrenheit (minus 4 degrees Celsius), a temperature easily reached by a home refrigerator freezer. Pfizer's vaccine required storage in specialized ultracold freezers capable of cooling below minus 94 degrees Fahrenheit (minus 70 degrees Celsius). Moderna also says its vaccine will remain potent for up to 30 days at normal refrigerated temperatures, which should ease distribution.
Both companies' vaccine studies managed to recruit a reasonably diverse group of people. Moderna reports 6,000 enrollees who identified as Hispanic or Latinx and more than 3,000 participants who identified as Black or African American, as well as 7,000 people older than 65, and 5,000 with high-risk chronic diseases.
Pfizer and Moderna are still gathering safety data the Food and Drug Administration has said is necessary for consideration of an emergency use authorization that would allow the companies to distribute the vaccine during the pandemic.
Side effects seen for the Moderna vaccine at the interim analysis included pain at the injection site, fatigue and aching muscles and joints. The data safety and monitoring board didn't identify "any significant safety concerns."
Moderna said it intends to file "in the coming weeks" with the FDA for authorization of the company's vaccine for emergency use.
The federal Operation Warp Speed project to hasten development of COVID-19 vaccines awarded Moderna a $1.5 billion contract in August to ramp up manufacturing and deliver 100 million vaccine doses, enough for 50 million people. The government has an option to buy up to 400 million more doses.
Moderna said Monday that it expects to be able to ship about 20 million vaccine doses in the U.S. by the end of 2020. Next year, the company said it expects to be able to make 500 million to 1 billion doses worldwide.
The research and development of the Moderna vaccine was aided by $955 million in federal funding from the Biomedical Advanced Research and Development Authority. Moderna has also been developing this vaccine alongside the National Institute for Allergy and Infectious Diseases, which in July told NPR it expects to spend about $410 million on the effort.