While the caseload is higher than last year’s, it is only a fraction of the population at risk, he argued.

“Most of these new cases are occurring in areas where, until now, we didn’t recommend immunization,” he said.

To overcome suspicion of the vaccine and frustration with long lines at clinics, vaccinators have begun going door-to-door or using tents shifted from one neighborhood to another. There, they hope face-to-face chats will succeed where other efforts have failed.

Lucia Elena de Paula, 36, explained her fears to a nurse, saying, “I saw a video on WhatsApp with a girl who said she was paralyzed after taking the vaccine.”

But after a few soothing words from a staff member, she agreed to get the shot.

After dragging her 10-year-old grandson into a gym where the vaccines sat on an exercise bench, Aparecida Caldeira, 61, explained why she had hesitated.

“When we went to the clinic in January, the lines were just too long,” she said. “I’m so grateful they came here. But that’s just typical in Brazil — waiting to do everything at the last minute.”