The findings are reassuring because immunity tends to weaken with age, Dr. Evan Anderson, one of the study’s lead researchers from Emory University in Atlanta, said in a phone interview.

The study was an extension of Moderna’s Phase I safety trial, first conducted in individuals aged 18-55. It tested two doses of Moderna’s vaccine – 25 micrograms and 100 micrograms – in 40 adults aged 56 to 70 and 71 and older.

Overall, the team found that in older adults who received two injections of the 100 microgram dose 28 days apart, the vaccine produced immune responses roughly in line with those seen in younger adults.