Efficacy of a bivalent (D614 + B.1.351) SARS-CoV-2 recombinant protein vaccine with AS03 adjuvant in adults: a phase 3, parallel, randomised, modified double-blind, placebo-controlled trial
RCT (n=11,416) showed clinical efficacy (64.7%) of this beta variant-containing vaccine in protecting against different SARS-CoV-2 variants, including omicron (BA.1 & BA.2), with 121 symptomatic COVID-19 cases reported ≥14 days after second dose (32 vaccine vs 89 placebo group).
Source:
The Lancet Respiratory Medicine
SPS commentary:
The researchers state that currently available vaccines are less effective against COVID-19 due to newly emergent SARS-CoV-2 variants of concern (including the omicron [BA.1, BA.2, BA.4, and BA.5] variants and subvariants [BQ.1.1 and XBB]). Therefore, vaccines with variant strains have been developed subsequently to provide cross-protection against emerging variants. However, no data are available on whether an alternative non-omicron variant vaccine can provide cross-protective efficacy against omicron variants. The bivalent vaccine in this study contains a stabilised SARS-CoV-2 pre-fusion S proteins from both the ancestral D614 and the beta (B.1.351) variant, with the GSK AS03 adjuvant system (CoV2 preS dTM-AS03 [D614 + B.1.351]).
A commentary notes that thought the data clearly show that the bivalent vaccine is protective against symptomatic SARS-CoV-2 infection, the absence of a monovalent comparator means that attributing added protection to the inclusion of the beta variant is pure speculation at this point. It points out that the results of this trial are being published a full 2 years after the beta variant was fully replaced by the delta (B.1.617.2) variant, which was then subsequently replaced by omicron variants. It adds that the intervening period represents the time needed to switch to the manufacture of a new vaccine and fully validate its efficacy, and highlights the futility of attempting to release COVID-19 vaccines into widespread use that match circulating strains. It also highlights that in the absence of clear data showing improved efficacy of strain-matched vaccines, there is a risk that focusing on updates to vaccine antigen composition puts at risk alternatives with unique advantages yet to be fully exploited. As an example, it notes that one such advantage of protein-based subunit vaccines is the lower rate of solicited systemic reactions.