We're selling the coronavirus vaccine short

The effectiveness of the COVID-19 vaccines against disease and death has been remarkable, but too much emphasis on the unknowns about transmission could discourage people from getting vaccinated.

Why it matters: The best vaccine in the world won't stop the pandemic if too few people take it.

• While some uncertainty remains about their impact on spread and their effectiveness against new variants — not to mention distribution problems — the biggest challenge may be how to talk about vaccines to those who think the shots aren't worth it.

Driving the news: On Friday, Johnson & Johnson announced that its one-shot vaccine proved 66% effective against COVID-19.

• That's less than the 95% protection provided by earlier mRNA vaccines from Moderna and Pfizer, but the headline numbers underplay the effect the new shot could have on controlling the pandemic.
• In a more than 44,000-person study conducted across multiple countries, the Johnson & Johnson vaccine prevented 85% of severe infections and 100% of hospitalizations and deaths. Those are the outcomes, of course, that turn COVID-19 from an annoyance to a global catastrophe.

Yes, but: While demand for coronavirus vaccines exceeds supply right now, recent polling suggests more than half of the U.S. would still decline or delay a shot if one were available to them now for free.

• Some of that hesitancy is driven by general skepticism about vaccines and specific concerns about the new shots, despite reams of scientific data underscoring their safety.
• But it doesn't help that much of the messaging around the vaccines emphasizes uncertainty about their effect on transmission as opposed to disease and death.
• It also pushes the idea that life shouldn't change for the vaccinated even after they've gotten all of their shots, as they might have to keep wearing masks and social distancing afterward.
• The CDC says "not enough information is currently available" to say when or if it will stop recommending masks and distancing for the vaccinated.
• That messaging has been seized on by those who feel the personal threat of getting COVID-19 doesn't justify accepting a shot, and by groups who want to delay a return to normal even after vaccines have become much more available.

Context: It's true that scientists have yet to produce clear data on how the vaccines might impact transmission, which can occur asymptomatically with COVID-19. The clinical studies that led to the vaccines' approval focused on disease and death.

• But as Patrick Vallance, the U.K.'s chief medical officer, told reporters recently, "You don't have vaccines of this efficacy without there being some effect on transmission."
• A study of Moderna's COVID-19 vaccine in monkeys suggested it will reduce if not totally prevent onward transmission of the virus, and other research has shown similar effects with AstraZeneca's and Pfizer's vaccines.

Details: We won't know for sure whether the vaccines halt the chain of infection as well as prevent disease until scientists can carry out focused studies and observe the effects of growing vaccination numbers.

• Concerns also remain about the impact that more contagious variants will have on the effectiveness of vaccines.
• But none of this should be considered a reason to forego a shot for populations it has been approved for.

Yet some scientists worry that is precisely the message many hesitant about the vaccines will take away from the headlines.

• "Trying to eliminate even the lowest-risk changes in behavior both underestimates people’s need to be close to one another and discourages the very thing that will get everyone out of this mess: vaccine uptake," Harvard epidemiologist Julia Marcus wrote recently in the Atlantic.
• The reality is that the vaccine will need to be actively sold to many Americans, yet as infectious-disease specialist Aaron Richterman told the New York Times, "We're underselling the vaccine."

Flashback: To some scientists, the problems around vaccine messaging are reminiscent of the confusion around masks at the start of the pandemic, when medical experts — in part out of concern they would be misused — initially discouraged their use.

• That mistake worsened the pandemic and did lasting damage to public trust in science.

The bottom line: Public health is a delicate dance, one that requires experts to balance scientific rigor — which demands clear evidence that is often lacking in the midst of a crisis — with the need to shepherd an often stubborn public.

• But right now, Americans need a clear message about the public and personal benefit of vaccination, lest we miss our best chance to stop this catastrophe.