Moderna Inc's experimental Covid-19 vaccine is more stable than expected at temperatures that ordinary refrigerators can provide and can be distributed using existing cold-chain shipping and storage infrastructure.
That opens the door for its early use in hard to reach places that might not be appropriate for Pfizer Inc's vaccine which needs ultra-cold storage.
Here are details of how it could be distributed.
HOW COLD IS COLD STORAGE?
Moderna's vaccine is stable for up to six months at a temperature of minus 20 degrees Celsius (-4 F), about home freezer levels, when shipped and stored.
The company said it expects the vaccine to be stable when kept at standard refrigerator temperatures of 2 to 8 degrees Celsius for 30 days, up from an initial projection of 7 days. The vaccine will be distributed in 10-dose vials and can be kept at room temperature for up to 12 hours after thawing.
By comparison, Pfizer's vaccine can be transported and stored for up to 6 months at minus 70 degrees Celsius (-94 F). It can be stored at standard refrigerator temperatures for up to five days.
WHEN WILL IT BE SHIPPED, TO WHOM?
Moderna's vaccine will be distributed by the US government's Operation Warp Speed program. US health officials have said that at first they are most likely to distribute vaccines to healthcare workers, people who are in nursing homes, first responders and those with health conditions who are high-risk.
Most Americans will be inoculated in May or June, according to Dr. Anthony Fauci, the nation's top infectious disease expert.
Under Operation Warp Speed's distribution plan, the first group of shots will likely be distributed to and administered in closed settings, like hospitals and nursing homes.
After January, as supply increases, those shots will start to be available in pharmacies, doctors offices and clinics as well as mobile clinics, the plan shows.
Health officials have said it will be easier to use Moderna's vaccine in these settings than Pfizer's.
HOW WELL DOES THE MODERNA VACCINE WORK?
Moderna on Monday said its vaccine was 94.5% effective at preventing Covid-19 based on early results from large studies. That is similar to Pfizer's which the US drugmaker has said is more than 90% effective.
Moderna data also showed the vaccine was capable of helping prevent severe cases of Covid-19, and it represented volunteers from diverse communities.