The publication of positive results from AstraZeneca’s coronavirus vaccine trial in the United States on Monday boosted expectations that the drugmaker would be able to put a rocky rollout behind it. However, US officials released an unprecedented statement only hours later, expressing concern that the company had used “outdated information” from its analysis and that it may have given “an inaccurate view of the efficacy results.”

On Tuesday, a company spokesperson said the company was “looking into it.”

Experts said the latest blunder, when combined with previous data reporting errors and a recent blood clot scare, could cause long-term harm to the vaccine, which is critical to global efforts to stop the pandemic, and erode vaccine trust more generally.

Dr. Paul Hunter, a professor of medicine at the University of East Anglia, said, “I doubt it was (US officials’) intention to intentionally undermine confidence in the AstraZeneca vaccine.” “However, this is likely to increase vaccine apprehension.”

Hunter stressed that the severity of the problem was unknown. But this isn’t the first time the business has had issues.

Parts of the vaccine’s first big trial, which Britain used to approve it, were tainted by a manufacturing error that researchers didn’t acknowledge right away. Due to a lack of evidence on how well the vaccine protected older citizens, some countries initially limited its use to younger populations before changing their minds. In addition, US officials halted an AstraZeneca trial for an unprecedented six weeks as they investigated issues identified in the United Kingdom before concluding that the vaccine was not to blame.

After reports of rare blood clots in some people who took the AstraZeneca injection, more than a dozen countries briefly suspended their use — against the advice of international health agencies — last week. Although the European Medicines Agency concluded that the shot had little effect on the overall incidence of clots, the unwelcome publicity seems to have left its mark.

Since so many people are opposing the vaccine, a top official in Norway warned on Monday that it might not be possible to restart its use.

Marte Kvittum Tangen, the president of a Norwegian doctors’ group, told broadcaster NRK that “people specifically say they do not want the AstraZeneca vaccine.”

In Bucharest, Romania, vaccination coordinator Valeriu Gheorghita said 33,000 AstraZeneca immunization appointments were cancelled in less than 24 hours, and about a third of the 10,000 people who were supposed to get the vaccine did not turn up. On Monday, a sprawling exhibition center in Belgrade, Serbia, set up for people to get the AstraZeneca vaccine was largely deserted.

“Unfortunately, interpretation is more important than science,” said Dr. Bharat Pankhania, an infectious diseases expert at the University of Exeter in the United Kingdom.

“We have now seen that the AstraZeneca vaccine offers safety and is safe on many parameters,” he said. “However, the public narrative has not been as clear.”

The misunderstanding is exemplified by France.

President Emmanuel Macron of France initially said that the vaccine was ineffective for older people before retracting his statement. Despite this, France only approved AstraZeneca’s vaccine for adults aged 65 and up, citing a lack of evidence. The government then changed its mind, citing new evidence, and declared it safe for all adults. However, after reports of unusual blood clots in some vaccine patients, the government decided to stop giving the injection. AstraZeneca was restarted in France for those under the age of 55.

The jarring messages arrive at a time when France, like much of continental Europe, is struggling to accelerate its vaccination campaign while also dealing with a surge in cases that is threatening to overwhelm hospitals and cause new lockdowns.

When the company revealed on Monday that the shot was around 79 percent successful in stopping symptomatic COVID-19 and that there were no serious illnesses or hospitalizations among vaccinated volunteers, compared to five such cases in participants who received dummy shots, experts expressed hope that the company could step past its problems.

The data, according to Mene Pangalos, head of AstraZeneca’s biopharmaceuticals research and development, “puts to bed any doubts.”

However, the Data and Safety Monitoring Board experts from the US National Institutes of Health expressed concern about the information published in the early hours of Tuesday.

According to a statement released by a branch of the NIH, “we encourage the organization to collaborate with the DSMB to review the efficacy data and ensure the most reliable, up-to-date efficacy data is made public.”

And if the organization corrects the error, it will have long-term consequences.

A virologist at the University of Leicester, Julian Tang, cited the decades-long debate about the measles vaccine as a cautionary story.

He said that there was “absolutely no proof” that the (measles, mumps, and rubella) vaccine induced autism. Despite the fact the the paper that made that point was retracted, Tang claims that some people are still concerned about the vaccine.

In Europe, there is lukewarm support for the AstraZeneca vaccine, in comparison to governments in developed countries that are in dire need of supplies. AstraZeneca’s vaccine is projected to be widely used in developing countries because it is less expensive and easier to store than many competitors’.

According to Dr. Bruce Aylward, a senior advisor at the World Health Organisation, the UN agency has a long list of countries that are “extremely eager” to get the vaccine as soon as possible. He said, “We simply cannot get enough of it.”

However, some experts are concerned that European skepticism could potentially cast a pall over the vaccine worldwide. They suggested that a green light from the US Food and Drug Administration might reassure a jittery public about the shot.

“If the US regulator looks at this data and approves AstraZeneca, it will have a lot of clout,” Jimmy Whitworth, an international public health professor at the London School of Hygiene and Tropical Medicine, said.

AstraZeneca said that it would send its data to the FDA in a matter of weeks.

It’s still probable that the vaccine will dispel any concerns. Rui Manuel Martins, 68, of a vaccination center in Lisbon, dismissed the worries, claiming that millions of people had been immunized with very few side effects.

Before taking his first dose, he said, “There are still some cases of people refusing any medications.” “It’s safer to be vaccinated than not to be vaccinated.”