Here’s what worries scientists:

—FDA regulators will likely face enormous political pressure to approve a vaccine, even one that’s not proven safe and effective.

—A vaccine that’s less effective than billed could cause wider spread of the pandemic, Michael S. Kinch, director of the Centers for Research Innovation in Biotechnology and Drug Discovery at Washington University in St. Louis, writes in Stat News.

“A merely short-term effect could encourage vaccinated individuals to resume risky behaviors, which would all but guarantee that the epidemic endures,” argues Kinch, who is also a professor of biochemistry and molecular biophysics.

—A vaccine would likely erode compliance of social distancing and mask wearing, measures that are proven effective against spread of the virus.