A week after Pfizer reported its COVID-19 vaccine is more than 90 percent effective, biotechnology company Moderna has revealed similar efficacy from its own novel vaccine candidate. Both vaccines use a still experimental mRNA technology but experts are suggesting the big challenge ahead will be overcoming the logistical hurdles in carrying out mass vaccinations.
Moderna’s COVID-19 vaccine was the very first to begin Phase 1 human trials back in mid-March. The extraordinary pace of development was unprecedented, and it was underpinned by a new kind of vaccine technology.
mRNA vaccines are completely different to traditional vaccines, which often administer a weakened form of the virus to help train the immune system to recognize it. Instead, mRNA vaccines essentially deliver a manufacturing blueprint to cells in the form of RNA, directing them to produce a viral protein. The immune system then learns to recognize and attack this foreign protein so when a body is subsequently invaded by the targeted virus there are antibodies already trained to respond. Both the Pfizer and Modern COVID-19 vaccines utilize this mRNA technology.
As with Pfizer’s announcement last week, the results are based on an interim data evaluation. So it is important to remember these large Phase 3 trials are still ongoing, and the data has not yet been peer-reviewed or published.
Having said that, Moderna’s preliminary trial data is remarkably similar to what Pfizer has reported. The trial has recruited around 30,000 subjects, half receiving a placebo. Two doses, administered several weeks apart, are necessary to achieve optimal protection.
The interim analysis was based on 95 confirmed COVID-19 cases, of which only five were found in the active vaccine group. This means, so far, the Moderna vaccine has an estimated efficacy of 94.5 percent.
Unlike Pfizer’s somewhat detail-free press release last week, Moderna has offered a little more specific information regarding side effects. Of particular note is a secondary endpoint tracking severe COVID-19 cases. The company reports 11 severe cases were detected in the trial, however, all were in the placebo group.
This indicates the vaccine may protect from severe disease outcomes. But, as the trial does not measure asymptomatic cases, it is still unclear whether the vaccine is preventing infection or if it is simply keeping the disease mild. This is an important distinction as it will determine how effectively the vaccine will stop the spread of the virus, and ultimately bring an end to this global pandemic.
“Given the general similarity of the vaccine target and the immunological responses observed for all vaccines, these data generally suggest that vaccination will protect against severe illness and thereby should protect people from needing hospitalization or from dying from COVID,” says Penny Ward, from King’s College London. “We still need to know if there is protection against infection, as the latter leads to herd protection while protection against illness has a value for an individual it will not prevent circulation of virus and risk of disease in unvaccinated persons, or in people not responding adequately to vaccination.”
One major hurdle raised by the Pfizer vaccine last week was its need for ultra-cold storage. The Pfizer mRNA vaccine needs to be kept at temperatures between -70 and -80 degrees C (-94 and -112 Fahrenheit). This will make distribution challenging in the best of conditions, but Moderna has revealed its vaccine can be safely stored in common refrigerator temperatures.
“We are pleased to submit these extended stability conditions for mRNA-1273 to regulators for approval,” suggests Moderna’s chief of technical operations Juan Andres. “The ability to store our vaccine for up to 6 months at -20° C including up to 30 days at normal refrigerator conditions after thawing is an important development and would enable simpler distribution and more flexibility to facilitate wider-scale vaccination in the United States and other parts of the world.”
The Moderna vaccine was developed with assistance from the US government’s National Institute of Allergy and Infectious Diseases (NIAID). Anthony Fauci, director of NIAID, suggests these early vaccine results are deeply encouraging and much higher than he expected.
“I had been saying I would be satisfied with a 75 percent effective vaccine,” Fauci said in a recent interview. “Aspirationally, you would like to see 90 - 95 percent, but I wasn’t expecting it. I thought we’d be good, but 94.5 percent is very impressive.”
Dozens of COVID-19 vaccines are currently in various stages of development. Although there are several different technologies being tested virtually all of them fundamentally shoot for the same target – training the immune system to recognize the unique spike protein on the surface of coronavirus cells. These early Phase 3 trial results offer an encouraging indication that this spike protein target will work, and this means a variety of vaccines in development should be effective.
Overcoming the logistical hurdles ahead will take unparalleled levels of global collaboration
The big challenge many experts are now looking to is that of manufacturing, distribution and administration. Charlie Weller, head of vaccines at the research charity Wellcome, suggests not only are there pragmatic hurdles in delivering effective vaccines to everyone across the globe, but actually getting people to take the vaccine could prove unexpectedly difficult.
“Overcoming the logistical hurdles ahead will take unparalleled levels of global collaboration,” says Weller. “We cannot underestimate the importance of building public understanding, trust and confidence, which will be strongest if the response is locally led. Covid-19 vaccines will face the largest and fastest vaccine manufacturing scale-up and roll-out in history but the light at the end of the tunnel is looking brighter.”
A striking Pew Research poll in September noted falling support in the United States for a COVID-19 vaccine. The poll found around half of those surveyed would either definitely, or probably, not take a COVID-19 vaccine if it were available today.
