US biotech firm Moderna on Monday announced its experimental vaccine against Covid-19 was almost 95 percent effective, marking a second major breakthrough in the quest to end the pandemic.
Moderna released early results from a clinical trial with more than 30,000 participants, after American pharmaceutical company Pfizer and its German partner BioNTech last week said their vaccine was 90 percent effective.
Both frontrunners are based on new technology that uses synthetic versions of molecules called "messenger RNA" to hack into human cells, and effectively turn them into vaccine-making factories.
"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," said Moderna CEO Stephane Bancel.
"Today's news of a second vaccine is further reason to feel hopeful," tweeted US President-elect Joe Biden, but he cautioned that its widespread distribution was months away.
"Until then, Americans need to continue to practice social-distancing and mask-wearing to get the virus under control," he said.
Moderna plans to submit applications for emergency approval around the world within weeks, and says it expects to have approximately 20 million doses ready to ship in the US by the end of the year.
The company, which has received US$2 billion from the US government under "Operation Warp Speed," added it is on track to manufacture between 500 million to a billion doses globally in 2021.
Global infections from Covid-19 have soared past 54 million with more than 1.3 million deaths since the virus emerged in China late last year.
US President Donald Trump also weighed in on Twitter, to take credit. "Please remember that these great discoveries, which will end the China Plague, all took place on my watch!"
Beginning of the end?
The Moderna vaccine, which was co-developed by the US National Institutes of Health, is given in two doses 28 days apart, and the preliminary results are based on the 95 of the 30,000 volunteers who fell ill with Covid-19.
Of the 95, 90 had been in the trial's placebo group, and five in the group that received the drug, called mRNA-1273, translating to an efficacy rate of 94.5 percent.
There were 11 people who fell severely ill, all of whom were in the placebo group.
A small fraction of people experienced severe symptoms such as fatigue, muscle and joint pains, or redness at the injection site, but these side-effects were short lasting.
"The light at the end of the tunnel just got even brighter," tweeted Atul Gawande, a member of Biden's coronavirus advisory board and a surgeon at a Harvard-affiliated hospital.
Crucially, Moderna also announced that its vaccine can remain stable at standard refrigerator temperatures of two degrees Celsius to eight degrees Celsius (36 degrees Fahrenheit to 46 degrees Fahrenheit) for 30 days.
The company added it could be kept in long-term storage at standard freezer temperatures of minus 20 degrees Celsius (minus four degrees Fahrenheit) for up to six months.
Pfizer's vaccine, on the other hand, needs to be stored in deep-freezer conditions of minus 70 degrees Celsius (minus 94 degrees Fahrenheit) which could complicate supply chain logistics, particularly in less developed countries.
On the downside, Moderna's vaccine has about three times more genetic material per dose than its Pfizer counterpart, Zoltan Kis, a research associate at Imperial College's Future Vaccine Manufacturing Hub, said. This would raise production costs and make it harder to scale-up.
The promising results of both vaccines are seen as a validation for mRNA technology, which has never before been brought to regulatory approval.
It works by providing human cells with the genetic instructions to make a surface protein of the coronavirus, which trains the immune system to recognise the real virus.
Making a traditional vaccine is a longer process that normally involves developing a weakened form of a pathogen.
It is not yet clear how long lasting the protection will be from either the Moderna or Pfizer vaccines, nor how well they work for the elderly, the age-group at highest risk from Covid-19.
Another open question is whether they stop people who are exposed to the virus from transmitting it on to the other people, even though they may be themselves protected from the disease.
by Issam Ahmed, AFP