New Zealand wants a 90% vaccination rate. Street gangs may hold the key.

Rawiri Jansen, a Maori doctor, had an urgent message for the 150 people, mostly patch-wearing members of New Zealand’s plentiful street gangs and their families, who sat before him on a bright Saturday afternoon.

Covid-19 is coming for them, he said. Cases in New Zealand’s hospitals are rising rapidly. Soon, dozens of new infections a day might become hundreds or even a thousand. People will die. And vaccination is the only defense. “When your doctors are scared, you should be scared,” he said.

By the end of the day, after an exhaustive question-and-answer session with other health professionals, roughly a third of those present chose to receive a dose then and there.

Having abandoned its highly successful “Covid-zero” elimination strategy in response to an outbreak of the Delta variant, New Zealand is undergoing a difficult transition to trying to keep coronavirus cases as low as possible. On Friday, the country set a target of getting at least 90 percent of the eligible population fully vaccinated — a goal, the highest in the developed world, whose success hinges on persuading people like those who gathered to hear Dr. Jansen.

Already, 86 percent of the eligible population has received at least one dose. But the final few percent are the most difficult to reach, and one group of particular concern is the gang community, many of whose members are Maori or Pacific Islanders, who make up about a quarter of the overall population. In the past two months, multiple outbreaks have been reported among gangs, a subset of the population less likely to comply with official vaccination efforts, forcing officials to cooperate with gang leaders to reach their communities.