Scientists are demanding to know why astrazenecas trial of its covid-19 vaccine is still on hold in the us while it has been restarted elsewhere, worrying it could damage public trust.

The trial was originally halted because an uk participant developed a serious inflammatory condition. in the us, it has been on hold for almost two weeks, while trials in other countries including the uk have restarted.

Ashish jha, dean of the school of public health at brown university, said: normally, companies wouldnt give out information in the middle of a trial, but this is an exceptional case and we need to have radical transparency. otherwise, there is a risk the public will lose confidence in the whole process.

Astrazeneca is telling participants in resumed trials that the unexplained neurological symptoms were either unlikely to be associated with the vaccine or that there was insufficient evidence to say whether they were or were not associated, and so independent reviewers had recommended that vaccinations continue. clinical trials do not usually publish data before hitting pre-determined milestones.

The process to approve a vaccine in the us has become highly political, with critics accusing the trump administration of trying to rush out a vaccine before novembers presidential election.

As the political argument has intensified, polls show the public rapidly losing confidence that an eventual vaccine will be safe. the latest poll by pew research shows only half of americans now say they definitely or probably would be vaccinated at this time. that is a 21-point drop from may.

Gigi gronvall, an immunologist and senior scholar at johns hopkins center for health security, said when developing a vaccine in such extraordinary times, the companies and regulators should be more open about why the us trial has not been restarted.

It's important for everyone to be transparent and honest, she said. eventually, it's the public who will either take this vaccine or not, so it is to their advantage to be transparent as possible.

Neither astrazeneca nor the us food and drug administration would explain why the trial has not restarted.

Vaccine makers including astrazeneca, pfizer and moderna have tried to be more transparent by publishing their trial protocols.

Peter hotez, a virologist and vaccine specialist at the baylor college of medicine, said the illness developed by the trial participant was likely to be unrelated to the vaccine, but warned that communication problems could make the public more likely to refuse a vaccine, even if it was safe and effective.

He said it was disastrous that details of the illness had been aired in a private call with astrazeneca and investors, and called for operation warp speed, the us government project to invest in covid-19 vaccines, to take over communications from pharmaceutical companies.

History tells us that we have several good vaccines that went unused because of communication failures and public misperceptions, he said. it's important to remember that we have a very active anti-vaccine, anti-science movement that began in the uk and has been amplified in america.