Opinion | A new covid booster shot will be criticized. But it is worth getting.

For all the amazing benefits of the mRNA coronavirus vaccines, there are limitations. The effectiveness wanes. New variants evolve faster than shots can be adjusted. Destructive disinformation about their safety lingers. Yet, the vaccines are critical to battling disease and death — and that also goes for the next generation of boosters coming soon. Critics might raise fresh concerns about these new shots, and there are some things the public should know. But the latest booster, as with all the previous shots, promises to be a life raft in dangerous seas.

Both Pfizer/BioNTech and Moderna have asked the government for emergency use authorization for a bivalent booster that would be based on the earlier vaccine as well as target the now-prevalent BA.4/5 subvariants. The Food and Drug Administration and the Centers for Disease Control and Prevention are expected to give a green light in coming days. The Pfizer dose is for those 12 years and older; Moderna’s for 18 and older. In both cases, before the booster, a patient must have taken the two primary doses. But the new booster will be administered to anyone who has none, one or two of the previous booster shots.

The advantage of the bivalent booster is that it has a better chance of protecting against the variant that dominates today. No one knows how much better, but experts say it could boost the levels of protection, as well as the duration and the breadth. Unfortunately, it is still a booster, and there might need to be more. Science is still chasing the goal of a pan-coronavirus vaccine that will last a long time.

What’s different this time is that this booster is being rolled out before human clinical trials are complete. (The trials are getting underway.) This is a bit of a gamble that past is prologue — that the experience with billions of doses of the earlier vaccines shows they are safe and effective. Also, tests in mice show that the boosters work, and this testing method has been used often in the past with the seasonal influenza vaccine. The new boosters are already in production and might show up for consumers in September.

Waiting for full clinical trial results might leave the booster well behind the curve if the virus mutates into a new variant. The trade-off — a booster that is currently relevant, with less clinical trial data — seems reasonable. Demanding both an effective vaccine and a full clinical trial “is simply a fantasy against this rapidly changing virus,” says epidemiologist Katelyn Jetelina. Yet policymakers must be vigilant. They hold a fragile public trust in their hands. Already, booster uptake has been inexcusably low. The government must be totally transparent about this choice and do nothing to add to vaccine hesitancy and doubts.

The federal government has ordered 175 million doses of the bivalent booster, but this might be the last one that is free. Congress has unwisely balked at more pandemic funding. While many people have insurance that will eventually cover vaccine costs, those without insurance or means might give up on the vaccine life raft altogether. That would be an unnecessary and avoidable tragedy.