Moderna said that its experimental COVID-19 vaccine induced immune responses in older adults similar to those in younger participants, offering hope that it will be effective in people considered to be at high risk for severe complications from the coronavirus.

Its candidate, mRNA-1273, is already in late-stage human trials testing its ability to safely prevent infection. The latest data from an early Phase I study includes analysis from 20 additional people detailing how the vaccine performed in older adults.

The analysis looked at subjects given the 100-microgram dose being tested in the much larger Phase III trial. Moderna said the immune responses in those aged between ages 56 and 70, above age 70 and those 18 to 55-years-old were similar.

The company has so far enrolled over 13,000 participants in its late-stage study. About 18 per cent of the total participants are Black, Latino, Native American or Alaska Native, groups that have been particularly hard hit by the pandemic, and are often underrepresented in clinical trials.

Companies and health officials also are working on ways to distribute COVID-19 vaccines, some of which must be shipped and stored at extremely cold temperatures.

Moderna’s vaccine has to be kept at minus 20 degrees Celsius for shipping and longer-term storage of up to six months, but it can be kept at regular refrigeration temperatures for up to 10 days. The vaccine will be distributed in 10-dose vials with no preservatives, the company said.

Moderna also informed that it is working to make the vaccine stable at higher temperatures.