These countries did well with COVID. So why are they slow on vaccines?

Now the roles have been reversed. These countries that largely subdued the virus are among the slowest in the developed world to vaccinate their residents, while countries like Britain and the United States that suffered grievous outbreaks are leapfrogging ahead with inoculations.

The United States has fully vaccinated close to one-quarter of the population, and Britain has given first shots to nearly half its residents. By contrast, Australia and South Korea have vaccinated less than 3% of their populations, and in Japan and New Zealand, not even 1% of the population has received a shot.

To some extent, the laggards are taking advantage of the luxury of time that their comparatively low infection and death counts afford. And they all rely on vaccines developed — and, for now, manufactured — elsewhere.

Now the delays risk unwinding their relative public health successes and postponing economic recoveries as highly contagious variants of the virus emerge and bottlenecks slow shipments of vaccines around the world.

“The very success in controlling disease reduces the motivation and effort expended in setting up rapid-fire immunization clinics,” said Robert Booy, an infectious diseases and vaccine expert at the University of Sydney in Australia. “When people are dying left, right and center, the need is obvious.

“We need to recognize the complacency that’s building,” Booy added. “We’re just one superspreading event away from trouble.”

Nowhere is that a greater risk than in Japan, which is contending with a rise in cases and deaths as the start of the postponed Tokyo Olympics is less than 100 days away.

The slow rollout in the Asia-Pacific region is starting to frustrate some residents who have grown weary of more than a year of restrictions on travel, restaurant outings and family gatherings. They are eager to exit the purgatory of these measures and get back to normal life, but relief may still be months away.

Erika Inoue, 24, who works at a research group in Tokyo that consults on projects for local governments and businesses, said she was envious of friends in the United States who had received their shots.

“Among my friends’ group, I’m the only one who hasn’t gotten vaccinated,” said Inoue, who is hoping to attend a friend’s wedding in Tunisia. “I cannot wait.”

Japan, South Korea and Australia have all fallen far behind the vaccination timelines they laid out months ago.

Some wards in Tokyo began administering shots to those older than 65 just this past week. In South Korea, where authorities initially said they would be able to vaccinate about 1 million people a day, they have averaged closer to 27,000 in the first three months vaccinating. This month, Australian health officials dropped a goal of vaccinating the country’s entire population by the end of the year.

In Australia and Japan, authorities have blamed supply problems from Europe for the slow rollout. Australia has said the European Union failed to deliver 3.1 million doses of the AstraZeneca vaccine. A spokesperson for the European Commission said that only 250,000 doses had been withheld from Australia by Italy in March, but officials in Australia say the reality is that the rest of the doses, blocked or not, simply have not arrived.

Australia has faced further complications as it has advised against giving the AstraZeneca vaccine to people younger than 50 after reports of very rare blood clots.

In Japan, Taro Kono, the Cabinet minister overseeing the vaccination program, has complained that the European Union grants approval on a shipment-by-shipment basis rather than approving multiple shipments at once. “We could get our vaccines stopped by the EU,” he said, citing the withheld doses to Australia.

The European Union has authorized shipments of more than 39 million doses to Japan, Patricia Flor, the union’s ambassador to Japan, said in an interview. “I would totally and absolutely reject any statement which would say that the way the vaccination campaign in Japan is going is related in any way to delays or problems in deliveries from the EU,” she said.

Supply issues or not, other factors have also led to delays. Japan requires domestic clinical trials of new vaccines, and in both Japan and South Korea, officials have proceeded carefully to persuade people who say they are reluctant to get vaccinated right away.

Kim Minho, 27, a researcher at the Institute of Engineering Research in Seoul, South Korea, said the government had depended too heavily on measures like social distancing to curb infection rates. “Korea was late to the vaccine party,” he said.

A similar dynamic is true in Japan. Experts said the country might simply have failed to negotiate contracts requiring early deliveries of vaccines doses. In a statement, Pfizer said it would deliver on its commitment of 144 million doses to Japan by the end of 2021. Japan has yet to give regulatory approval to the Moderna or AstraZeneca vaccines, although it has contracted with both companies to buy millions of doses.

Health ministry officials “are professionals about public health,” said Dr. Hiroyuki Moriuchi, a professor of global health at Nagasaki University. “But when it comes to business or contract writing, they are not professionals or experts in this area.

“If Japan had a firm consciousness that this is a sense of crisis,” he added, “they would not have relied only on health ministry officials” to negotiate such contracts.