RUSSIAN PRESIDENT Vladimir Putin may have pulled off a good public relations stunt on Tuesday, at least for the short term. He announced that the Gamaleya Research Institute of Epidemiology and Microbiology is first in the world to win approval for a coronavirus vaccine. The announcement of the new Sputnik V vaccine recalled the glory of the Soviet Union’s pioneering orbital satellite. Let’s hope it works, but given the unknowns, Mr. Putin’s showy launch and promise of rapid distribution are reason for worry.

Along with the difficulty of creating an effective vaccine and the challenges of testing, manufacturing and distributing it, it is essential to build and maintain public confidence so enough people will accept inoculation to create herd immunity against the virus, perhaps two-thirds of a population. Many experimental vaccines are likely to fail in research or clinical trials; this is science at work. But that makes it doubly important that confidence not be shaken by hasty or unnecessary political mistakes.

The Russian Sputnik V vaccine has so far been tested in trials with a small number of people; the institute planned to use only 38 volunteers. No data has been published. Russia said next will be a larger trial of 2,000 people. This is well short of the rigorous Phase 3 clinical trials with tens of thousands of people that are established practice in the U.S. and European vaccine regulatory systems. If something goes wrong — serious side effects or inability to block the virus or mitigate symptoms — Mr. Putin’s glory-seeking will dissolve into mass disappointment.

Vaccine hesitancy is on the rise around the world, propelled in part by an irresponsible anti-vaccine movement that spreads suspicion and conspiracy theories, often on social media. In a Gallup Poll survey taken July 20 to Aug. 2, only 65 percent of those questioned said they would take a coronavirus vaccine, while 35 percent said they would not. Compare that with real-world behavior: In the United States, 91.5 percent of children aged 19 to 35 months get the measles, mumps and rubella shot; 92.7 percent get immunized against polio. Interestingly, Gallup points out that when adults were asked in 1954 about the then-new polio vaccine, just 60 percent said they would take it, while 31 percent said they would not.

The Trump administration’s crash vaccine effort — Operation Warp Speed — gives rise to worry that someone might try to cut corners in advance of the November election. Food and Drug Administration Commissioner Stephen M. Hahn pledged in these pages recently that approval will be “based solely on good science and data.” Dr. Hahn must remain on guard against the kind of White House pressure that was applied on behalf of hydroxychloroquine.

To have any hope of beating the pandemic, vaccine development must retain public confidence. A slip-up that creates even a ripple of doubt could have catastrophic consequences.

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