NEW YORK — Far beyond the United States and Europe, the safety scares engulfing the AstraZeneca and Johnson & Johnson vaccines have jeopardised campaigns to inoculate the world, undercutting faith in two sorely needed shots and threatening to prolong the coronavirus pandemic in countries that can ill afford to be choosy about vaccines.

With new infections surging on nearly every continent, signs that the vaccination drive is in peril are emerging, most disconcertingly in Africa.

In Malawi, people are asking doctors how to expunge the AstraZeneca vaccine from their bodies.

In South Africa, health officials have paused giving the Johnson & Johnson shot, the only one they have, a repeat blow after dropping AstraZeneca from their arsenal in February.

And in Congo, not a single person has been vaccinated, despite 1.7 million doses of the AstraZeneca shot languishing in the country since March 2.

In those countries and others, Western colonialism and unethical medical practices have left a residue of mistrust in vaccines, which could harden if the perception takes hold that rich countries are dumping second-rate shots on the global south.

Already, doctors say, the recent pauses have vindicated vaccine sceptics and made many others feel duped.

“People, especially those who were vaccinated, felt like they had been tricked in a way; they were asking, ‘How do we get rid of the vaccine in our body?’” said Dr Precious Makiyi, a doctor and behavioural scientist in Malawi, where health workers have been racing to empty their shelves of nearly expired AstraZeneca doses.

“We fought so hard with vaccine messaging, but what has happened this past week has brought us back to square zero.”

African health officials have reacted with fury at the breezy reassurances of American and European lawmakers that people denied the AstraZeneca or Johnson & Johnson shots could be given another vaccine. In much of the world, there are no other vaccines.

And even as American health officials stressed that they paused use of the Johnson & Johnson vaccine Tuesday in “an abundance of caution,” they forced global health officials to begin crafting the difficult case that shots unsafe for the world’s rich were still suited to its poor.

“It’s sending vaccine confidence into a crater,” Dr Ayoade Alakija, co-chair of the African Union’s Africa Vaccine Delivery Alliance, said of rich countries’ actions.

“It’s irresponsible messaging, and it speaks to the selfishness of the moment that there wouldn’t be more consultation and communication.”

What rich countries call caution, poorer nations will experience as a devastating gamble with the lives of their citizens. “Out of an abundance of caution, let us not destroy vaccine confidence in places that only have access to one type of vaccine,” Dr Alakija said.

The AstraZeneca and Johnson & Johnson vaccines, cheaper and easier to store than the alternatives, are mainstays of global inoculations. AstraZeneca’s shot is being used in at least 118 countries. Lately, amid shortages of that vaccine, some regions have pivoted to Johnson & Johnson’s; two weeks ago, the African Union acquired 400 million doses.

Together, the two vaccines account for one-third of the portfolio of Covax, the international effort to procure and distribute vaccines.

But it is becoming more apparent by the day that those shots, built on a relatively rugged vaccine platform, are becoming afterthoughts in wealthy nations. After cancelling Johnson & Johnson appointments over concerns about rare blood clots, US states offered people the pricier Pfizer or Moderna vaccines instead.

The European Union said Wednesday that it had acquired another 50 million doses of the Pfizer vaccine, allowing it to curb use of AstraZeneca’s vaccine and phase it out altogether next year.

Those decisions, intended for domestic audiences, have nevertheless reverberated in countries where variants are spreading, physical distancing is a luxury, and there is no choice of shots.

Health officials fear that any setbacks in vaccinations could sow the seeds of the next calamitous outbreak, one that deluges hospitals and exports new mutations around the world. In those places, doctors said, the math is obvious: Many more people will die without the AstraZeneca and Johnson & Johnson vaccines than with them.

Amid the clotting concerns, the World Health Organization and African Union have not wavered in recommending the use of the AstraZeneca and Johnson & Johnson vaccines.

In Britain, AstraZeneca’s vaccine remains the backbone of the country’s speedy inoculation campaign, despite people younger than 30 being offered alternatives. Congo, after spurning the AstraZeneca shot in light of unease in Europe, said Tuesday that it would launch the much-delayed inoculations next week.

And in Dakar, the capital of Senegal, people continued to line up on wooden benches Wednesday for the AstraZeneca shot as they watched their children run through the corridors of a medical center.

“We don’t have a choice,” said Mr Alioune Badara Diagne, 34, who lives in the city’s lively Ouakam neighbourhood. Despite talk of vaccination pauses in wealthy nations and rumours of vaccine-makers using Africans as “guinea pigs,” he said, Westerners themselves were continuing to be injected.

He added, “The vaccine is our only hope.”

But in much of the world, the US regulators who endorsed Tuesday’s pause on Johnson & Johnson vaccinations act as sort of surrogate decision-makers on drugs and vaccines, giving their hesitation extra weight in African nations.

“I became even more sceptical when I heard that the United States suspended Johnson & Johnson,” said Mr Lawmond Lawse Nwehla, 32, an engineer in Dakar. “They said it was effective, and then they stopped it. So I wonder why.”

In immediately pausing the use of Johnson & Johnson’s shot, US regulators reacted more aggressively than did their British counterparts, who backed the AstraZeneca vaccine even as they investigated clotting cases.

South Africa immediately copied the US' pause on Johnson & Johnson vaccinations, infuriating doctors who are still clamoring for shots, especially in remote parts of the country. In February, health officials dropped the AstraZeneca vaccine over its limited efficacy against a dangerous variant there.

To date, only half of one per cent of the population is vaccinated, and a mere 10,000 shots are being given each day. At that rate, it could take weeks, if not longer, for a single rare blood-clotting case to emerge, said Dr Jeremy Nel, an infectious disease doctor in Johannesburg.

He was dismayed by the decision to pause shots, given the risk to vaccine confidence in a country where two-fifths of the people say they have no intention of being vaccinated.

“The slower you go, that failure is measured in death,” Dr Nel said. “Even if you delay for a week, there is a nontrivial chance that will cost lives.”

In Kenya, where enthusiasm for vaccines is high in cities but perilously low in rural areas, “the story about blood clots from Europe could not have come at a worse time,” said CDr atherine Kyobutungi, director of the African Population and Health Research Center there.

“Even those who were perhaps on the fence and leaning toward getting vaccinated all of a sudden had second thoughts,” she said.

The US' pause on Johnson & Johnson shots promised a second media furor.

“When the FDA suspends, it makes headlines for days,” she said. “When it lifts the suspension, it doesn’t make as many headlines.” THE NEW YORK TIMES