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SARS-CoV-2 mRNA-1273 Vaccine in Older Adults
Quick Takes
- The mRNA-1273 vaccine for SARS-CoV-2 is tolerable and immunogenic in older adults.
- Data on prolonged immunogenicity and effectiveness in preventing severe COVID-19 are still lacking for this vulnerable population.
Study Questions:
How immunogenic is the messenger RNA vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA-1273 in older adults?
Methods:
The Moderna manufactured mRNA-1273 vaccine encodes a stabilized version of the SARS-CoV-2 full-length spike glycoprotein trimer (S-2P). The National Institute of Allergy and Infectious Diseases (NIAID)-sponsored initial phase 1 open-label clinical trial of mRNA-1273 was expanded to include 40 adults ≥56 years old who were administered a dose of 25 μg or 100 μg of the vaccine at days 1 and 29 of the study for a total of two doses. The participants were stratified by age groups: ages 56-70 (n = 20), and ages ≥71 (n = 20). No screening for past or current SARS-CoV-2 infection was performed at enrollment. Participants were followed until day 57 for adverse effects, quantification of antibody and neutralizing responses, and T-cell responses.
Results:
No serious adverse events were reported. The most common adverse events were headache, fatigue, myalgia, chills, and injection-site pain, occurring more frequently and with stronger intensity in those receiving the 100 μg dose. Immunoglobulin G (IgG) antibody titers to S-2P and receptor binding domain increased rapidly after vaccination in a dose-dependent fashion, with participants ≥71 years having higher titers compared to those ages 56-70 years. Similarly, a dose-dependent viral neutralization response was noted and similar in magnitude in both age groups and compared to that previously reported in participants ages 18-55 years. Neutralizing activity remained high for up to 4 weeks after the second dose of the vaccine. The vaccine elicited a strong CD4 cytokine response involving type 1 helper T (Th1) cells among participants in the two age subgroups who received the 100-μg dose, and among participants between the ages of 56 and 70 years who received the 25-μg dose.
Conclusions:
The mRNA-1273 vaccine is safe in older adults even at higher doses, and induced anti–SARS-CoV-2 immune responses successfully.
Perspective:
This substudy of the phase 1 clinical trial for Moderna’s mRNA-1273 vaccine, while small in sample size, provides reassuring findings regarding its tolerability and immunogenicity. The study of vaccines in the elderly is essential, for: 1) they represent the population at highest risk of severe illness and would benefit the most from an effective vaccine, 2) aging is associated with immune-senescence, or dysfunction of the immune system, and 3) accordingly, responses against vaccines for other diseases are attenuated in the elderly. In-vitro assessments of immunogenicity, however, does not necessarily translate to effectiveness in preventing coronavirus disease 2019 (COVID-19) or abrogating its severity. It is also unclear whether immunogenicity persists beyond the short period of the study. We await with cautious optimism data on the effectiveness of the vaccine.
Clinical Topics: COVID-19 Hub, Geriatric Cardiology, Prevention
Keywords: Coronavirus, Coronavirus Infections, COVID-19, Geriatrics, Immune Tolerance, Myalgia, Primary Prevention, Receptors, Cytokine, RNA, Messenger, severe acute respiratory syndrome coronavirus 2, Th1 Cells, Vaccination
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