Moderna’s COVID-19 Vaccine Candidate Elicits Immune Response in Older Adults

Interim data showed that both doses of mRNA-1273 elicited strong immune responses in older adults.

A phase 1 study evaluating the safety and immunogenicity of the vaccine candidate mRNA-1273 (Moderna) against coronavirus disease 2019 (COVID-19) showed that the vaccine elicited a strong immune response in older adults. 

The National Institute of Allergy and Infectious Diseases (NIADH)-led study initially reported positive interim results in May 2020 in 45 healthy adults aged 18 to 55 years. A month after the study was initiated, it was expanded to include older adults; the study enrolled 40 healthy volunteers in 2 cohorts: 56-70 years of age (n=20) and 71 years of age and older (n=20). Within each cohort, half the patients received a lower dose of vaccine (25mcg), while the other half received a higher dose (100mcg); the vaccine was administered intramuscularly on a 2-dose vaccination schedule, given 28 days apart. 

Interim data showed that both doses of mRNA-1273 elicited strong immune responses in older adults with robust binding and neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Immune responses were dose-dependent with the 100mcg dose eliciting higher binding and neutralizing antibody titers. Moreover, older adults achieved immune responses which were comparable to that seen in younger adults. 

At day 57, both doses of the vaccine induced dose-dependent binding antibody responses with geometric mean titers (GMT) above the median of those seen in convalescent sera from 41 patients with confirmed COVID-19 diagnosis. In the 25mcg dose group, the GMT was 323,945 (56-70 years) and 1,128,391 (71 years and older). In the 100mcg dose group, the GMT was 1,183,066 (56-70 years) and 3,638,522 (71 years and older). All participants showed serum neutralizing activity 14 days after the second vaccination. Both doses also elicited a strong Th1-biased CD4 T cell response across all age groups.

With regard to safety, mRNA-1273 was well tolerated with no serious adverse events reported through day 57. The most common solicited adverse events included fever, chills, headache, myalgia, and pain at the injection site, which were mild to moderate in severity. 

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.

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“These interim phase 1 data suggest that mRNA-1273, our vaccine candidate for the prevention of COVID-19, can generate neutralizing antibodies in older and elderly adults at levels comparable to those in younger adults,” said Tal Zaks, MD, PhD, Chief Medical Officer of Moderna. “Given the increased morbidity and mortality of COVID-19 in older and elderly adults, these data give us optimism in demonstrating mRNA-1273’s protection in this population, which is being evaluated in the phase 3 COVE study.”

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  1. Investigational COVID-19 vaccine well-tolerated and generates immune response in older adults. Accessed September 30, 2020. 
  2. Anderson EJ, Rouphael NG, Widge AT, et al. Safety and immunogenicity of SARS-CoV-2 mRNA-1273 vaccine in older adults. N Engl J Med. Published online September 29, 2020. doi: 10.1056/NEJMoa2028436.
  3. Moderna announces publication in The New England Journal of Medicine of interim results from older adult age cohorts in phase 1 study of its mRNA vaccine against COVID-19 (mRNA-1273). Accessed September 30, 2020.