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.
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 greater than or equal to 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 or more ( 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.
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 or more 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.
In conclusion, the mRNA-1273 vaccine is safe in older adults even at higher doses, and induced anti–SARS-CoV-2 immune responses successfully.
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. ( Xagena )
Source: The New England Journal of Medicine, 2020