Results from the Phase 1 trial of an investigational Covid-19 vaccine co-developed by researchers at the US National Institute of Allergy and Infectious Diseases (NIAID), and the American biotech company Moderna have shown that it is well-tolerated and generates a strong immune response in older adults.
The study, published in the New England Journal of Medicine, noted that the experimental vaccine, mRNA-1273, was well-tolerated by the older trial participants, who were over 55 years of age.
According to the researchers from NIAID, older adults are more vulnerable to complications of Covid-19 and are an important population for vaccination.
They said understanding how the vaccine affects this section of the population is a critical part of measuring its safety and efficacy.
The Phase 1 trial began on March 16, 2020, and was expanded to enroll older adults about one month later.
In its expansion, the scientists said the trial enrolled 40 healthy volunteers — 20 adults ages 56 to 70 years, and 20 adults ages 71 years and older.
Ten volunteers in each age group received a lower dose of the vaccine, and 10 participants in each age group received a higher dose.
After approximately one month, the researchers said the volunteers received a second dose of the same vaccine at the same dosage.
They said the volunteers attended clinic visits to track their responses to the vaccine, and assess safety throughout the study.
The research found that the investigational vaccine was well-tolerated in this older age group — although some volunteers experienced transient adverse effects, including fever and fatigue after vaccination.
According to the scientists, the participants exhibited a good immune response to the vaccine, with the blood of vaccinated volunteers containing robust binding and neutralizing antibodies against the coronavirus SARS-CoV-2.
They said the immune response to the vaccine seen in older volunteers was comparable to that seen in younger age groups.
The researchers said the study will continue to follow the older volunteers for approximately a year after the second vaccination to monitor the long-term effects of the vaccine.
The results from the Phase 1 trial further support testing of the investigational vaccine in older adults in an ongoing large Phase 3 trial, they added.