September 15, 2021Open Access
Safety and immunogenicity of SARS-CoV-2 variant mRNA vaccine boosters in healthy adults: an interim analysis
Structured PICO
Does a single booster dose of mRNA-1273 or variant-modified mRNAs improve neutralization titers against SARS-CoV-2 variants in healthy adults who previously received the mRNA-1273 primary series?
P
Population
80 healthy adults (four groups, n=20 per group) who received a two-dose primary series of the COVID-19 vaccine mRNA-1273 approximately 6 months earlier
I
Intervention
Single booster dose of mRNA-1273 or variant-modified mRNAs, including multivalent mRNA-1273.211
C
Comparator
Peak titers against wild-type D614G measured 1 month after the primary series (within-subject comparison)
O
Outcome
Safety and immunogenicity (neutralization titers against wild-type and variants)surrogate
A single booster dose of mRNA-1273 or variant-modified mRNAs safely increases neutralization titers against SARS-CoV-2 variants to levels comparable to or higher than peak titers after the primary series.
Abstract
The emergence of SARS-CoV-2 variants of concern (VOCs) and variants of interest (VOIs) with decreased susceptibility to neutralization has generated interest in assessments of booster doses and variant-specific vaccines. Clinical trial participants who received a two-dose primary series of the COVID-19 vaccine mRNA-1273 approximately 6 months earlier entered an open-label phase 2a study ( NCT04405076 ) to evaluate the primary objectives of safety and immunogenicity of a single booster dose of mRNA-1273 or variant-modified mRNAs, including multivalent mRNA-1273.211. As the trial is currently ongoing, this exploratory interim analysis includes preliminary descriptive results only of four booster groups (n = 20 per group). Immediately before the booster dose, neutralizing antibodies against wild-type D614G virus had waned (P < 0.0001) relative to peak titers against wild-type D614G measured 1 month after the primary series, and neutralization titers against B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) VOCs were either low or undetectable. Both the mRNA-1273 booster and variant-modified boosters were safe and well-tolerated. All boosters, including mRNA-1273, numerically increased neutralization titers against the wild-type D614G virus compared to peak titers against wild-type D614G measured 1 month after the primary series; significant increases were observed for mRNA-1273 and mRNA-1273.211 (P < 0.0001). In addition, all boosters increased neutralization titers against key VOCs and VOIs, including B.1.351, P.1. and B.1.617.2, that were statistically equivalent to peak titers measured after the primary vaccine series against wild-type D614G virus, with superior titers against some VOIs. This trial is ongoing.