COVID-19 Vaccine Candidate Well Tolerated in Older Adults

A messenger RNA (mRNA) coronavirus disease 2019 (COVID-19) vaccine was well tolerated in older adults, according to a recent study published in The New England Journal of Medicine.

The COVID-19 pandemic has caused over 1 million deaths worldwide and there have been more than 33.5 million confirmed cases, according to the World Health Organization. Older individuals are especially vulnerable, as increased incidences of illness and death have been associated with older age.

The phase 1 dose-escalation, open-label trial included 40 adults aged 56 years and older. The participants were split into 4 groups of 10 who were then divided by age—56 to 70 years of age and 71 years of age and older. Then, they were evenly assigned to receive 2 doses 28 days apart of either 25 μg or 100 μg of mRNA-1273. mRNA-1273 encodes the stabilized prefusion of severe acute respiratory syndrome coronavirus 2 spike protein (S-2P) in healthy adults, according to the study.

Adverse events (AEs) were most frequently fatigue, chills, headache, myalgia, and injection site pain. AEs were predominantly mild or moderate in severity and were more common after the second immunization, according to the study.

A higher dosage was found to be more effective, supporting that a higher dose be used in phase 3 vaccine trials. In the 56 to 70 years of age group who received the 25-μg dose, the anti-S-2P geometric mean titer (GMT) was 323,945 and whereas for the 71 years of age or older group it was 1,128,391. In patients who received the 100-μg dose, the GMT in the 2 age groups was between 1,183,066 and 3,638,522, respectively.

“In our study population of older participants (≥56 years of age), the two-dose vaccine series had an acceptable safety and reactogenicity profile at doses of both 25 μg and 100 μg with mostly mild-to-moderate local and systemic adverse events of short duration, which occurred predominantly after the second dose,” the study authors said in a joint statement via press release. “We did not observe systematic differences in the reactogenicity profile between this older cohort and participants between the ages of 18 and 55 years who had received the mRNA-1273 vaccine. Our findings were also similar to the results of other trials of mRNA vaccines involving younger adults.”

Due to the study’s small sample size, it is possible serious AEs were not captured, the researchers noted. A 13-month follow-up is planned for a longer duration of assessment of vaccine-related AEs.

REFERENCE:

Anderson, Evan J. MD, et al. Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults [Journal Article] The New England Journal of Medicine; September 29, 2020. DOI: 10.1056/NEJMoa2028436. Accessed September 30, 2020.