This late entry from Operation Warp Speed might have missed the window after the Omicron wave. If that variant’s race through the US population provides herd immunity against serious illness from COVID-19, new vaccines may not matter unless they target specific populations. However, one might argue that the new Sanofi/GSK could do just that — the vaccine-skeptic population, or at least the mRNA-skeptic subpopulation.

The delayed vaccine candidate comes with 100% protection against the worst outcomes, and decent numbers against acute cases in general:

Two doses of a new Covid vaccine that is based on a conventional approach achieved 100 percent efficacy against severe disease and hospitalizations, and it could be an effective booster after other Covid shots, the vaccine’s manufacturers announced on Wednesday.

The vaccine, made by the Europe-based pharmaceutical companies Sanofi and GSK, is one of four candidates that received billions of dollars for development from Operation Warp Speed, the Trump administration’s program to accelerate vaccines.

The new vaccine had an efficacy of 75 percent against moderate-to-severe disease. It showed 58 percent efficacy against symptomatic disease in its Phase 3 clinical trial. Although that number is lower than was observed for the mRNA vaccines made by Pfizer-BioNTech and Moderna in their initial trials, it is “in line with expected vaccine effectiveness in today’s environment dominated by variants of concern,” Sanofi and GSK said in a statement.

That is lower than the two mRNA vaccines as well as the adenovirus-based Johnson & Johnson. However, for those who mainly worry about the novel mRNA approach of Pfizer and Moderna, the Sanofi/GSK vaccine might convince them to get the two-dose inoculation. This vaccine candidate uses a modified form of the spike protein to stimulate the immune response rather than use genetic instructions to give the body a pattern for antibody production. As the New York Times points out, that is a more traditional path for viral vaccine development — and as it is less novel, it might convince skeptics to adopt it. It’s similar in approach to the Novavax vaccine candidate, which is before the FDA now.

The performance appears to be at least parallel to the Pfizer and Moderna vaccines. It actually produces more antibodies after the second shot than the two mRNA vaccines, according to a separate unpublished study. That doesn’t necessarily relate directly to real-world performance or lasting protection, two points that will only get clearly measured if/when the FDA issues an emergency-use authorization for its use.

However, conversion of vaccine skeptics is not the only potential benefit of the Sanofi/GSK candidate. It might work even better as a booster:

Used as a booster dose after one of the other available coronavirus vaccines, the Sanofi-GSK shot increased antibody levels by 18- to 30-fold. The companies intend to submit the vaccine for authorization to regulatory authorities in the United States and Europe, they said on Wednesday.

That’s all good news, as long as the clinical data matches the claims here. Also, this might end up being a replacement for the beleaguered J&J/Janssen vaccine for international distribution in developing nations. Like the J&J vaccine, this vaccine does not require special refrigeration, and that makes it a better choice than the mRNA vaccines. That matters in the US to some degree too, although not nearly as much; the benefit for J&J/Janssen here was mostly the one-and-done aspect that made follow-ups appear unnecessary until the data showed later that two shots were more effective. This is clearly a two-shot regimen for the unvaccinated, but apparently a single dose works very effectively as a booster.

At this point, the effort to get more Americans vaccinated and boosted seems like a stalemate. A new candidate at least has some potential for breaking through the trench lines, if it proves as safe and effective as Sanofi and GSK claim.