All of this must be done in the middle of a pandemic, in part by understaffed and overworked public-health departments. “We are trying to plan for the most complex vaccination program in human history after a year of complete exhaustion, with a chronically underfunded infrastructure and personnel who are still responsible for measles and sexually transmitted diseases and making sure your water is clean,” Moore said. Although Operation Warp Speed spent $18 billion on developing vaccines, the federal government initially offered states less than 2 percent of that—$340 million—to deploy them. The recently approved stimulus bill will add $8 billion for vaccine distribution, but, though welcome, those funds were needed months ago. And there is still no national vaccination strategy, said Saad Omer, a vaccinologist at Yale. The Trump administration has again left things up to the states, which have again concocted a hodgepodge of plans. “We shouldn’t be going into the biggest immunization effort this country has ever undertaken without a solid playbook and without enough resources to back the plays,” Omer said.

If vaccines are successfully distributed, Americans must agree to get them. As of earlier this month, 27 percent said they wouldn’t get a free COVID-19 vaccine, though that proportion had fallen since September. Many Americans are simply watching to see if the first vaccinations occur without issue. But here, the campaign might run into the same problem that vexes all prevention efforts: People don’t notice when they successfully avoid a disease, “but a negative reaction is memorable,” said Emily Brunson, an anthropologist at Texas State University. Because millions of people are getting vaccinated, many will coincidentally have heart attacks, strokes, or other problems soon after their shots. If viral social-media posts or half-baked news alerts link these health problems to the vaccines, while dwelling on every one of the expected side effects in real time, fear might unduly ground the campaign.