SARS-CoV-2 Moderna Vaccine, the mRNA-1273 Vaccine in Older Adults

Moderna published their safety and immunogenicity data from elderly patients in the New England Journal of Medicine, 29 September 2020, Anderson and others. 

They conducted a phase 1, dose escalation, open label trial of a messenger RNA vaccine mRNA-1273, which encoded the stabilised pre-fusion SARS-CoV-2 spike protein in healthy adults. 

The trial was expanded to include 40 older adults, who were stratified according to age 56 to 70 years or greater than or equal to 71 years.  All the participants were assigned sequentially to receive two doses of either 25 mcg or 100 mcg of vaccine administered 28 days apart. 

Results

Adverse events were predominantly mild or moderate in severity and most frequently included fatigue, chills, headache, myalgia and pain at the injection site. 

These adverse events were dose dependent and were more common after the second immunisation.

Binding antibody responses increased rapidly after the first immunisation.  By day 57, among the participants who had received the 25 mcg dose, the anti-S2P geometric mean titre was 323,945 amongst those between the ages of 56 to 70 and 1,128,291 amongst those who were 71 years of age or older. 

Among the participants who received the 100 mcg dose, the GMT in the two age subgroups were 1,183,066 and 3,638,522 respectively.

After the second immunisation, serum neutralising activity was detected in all the participants by multiple methods. 

Binding and neutralising antibody responses appeared to be similar to those previously reported among vaccine recipients between the age of 18 to 55 or above the median of the panel of controls who had donated convalescent serum. 

The vaccine also elicited a strong CD4 cytokine response involving type 1 helper T cells. 

Conclusions

In this small study involving older adults, adverse events associated with the mRNA-1273 vaccine were mainly mild or moderate. 

The 100 mcg dose induced higher binding and neutralising antibody titres than the 25 mcg dose which supported the use of the 100 mcg dose in a phase 3 vaccine trial. 

The London General Practice looks forward to a commercially available vaccine for all throughout the world.