Police in Brazil are investigating allegations that healthcare workers are giving fake Covid-19 inoculations, amid reports of nurses injecting people with empty syringes.
Cases of what local media are calling "wind vaccination" have been reported in four states, adding to the woes of the country's halting and uncoordinated immunisation programme, reports the Guardian.
Police announced a criminal investigation on Wednesday, amid speculation that the nurses were either anti-vaxxer conspiracy theorists, or were pocketing vaccine shots to be sold on the black market.
"This initially seemed an isolated case, but, although they are still exceptions, it is very concerning that we are seeing this in several places ," said Carla Domingues, an epidemiologist who coordinated Brazil's national immunisation programme between 2011 and 2019.
"Either these health professionals were poorly trained or they did it in bad faith. In both cases it is inadmissible," she added.
Rio state police said that if the vaccines had been misappropriated, those involved could be charged with embezzlement, which carries a sentence of up to 12 years in prison.
One video recorded by a relative and published in local media shows a nurse injecting an empty syringe in the arm of a 94-year-old woman at a drive-through vaccination site in the city of Petrópolis.
After the video went viral, the nurse was dismissed and investigations were launched by the municipality, the regional nursing council, and the local police.
"We have to wait for the conclusion of the investigation, but I don't believe it was intentional," said Aloísio Barbosa Filho, the secretary of health in Petrópolis.
The nurse had over 10 years' experience in the practice and was trained following immunisation protocols, according to the secretary.
"As it was the first days of vaccination, she might have felt some pressure and was more prone to error," Barbosa Filho said. "It is unacceptable anyway."
The secretary said that it was the only incident reported among more than 7,000 vaccines administered in Petrópolis, which has successfully immunised 2.7% of its population.
Brazil once boasted a world-renowned immunisation programme for diseases such as measles, polio, smallpox and tetanus, but it has faced a string of setbacks in the delivery of coronavirus vaccines.
"The [current] programme is totally uncoordinated," Domingues said. "The plan should be organized at the federal level, but the health ministry delegated it to regional authorities."
One month after Brazil kicked off its nationwide immunisation campaign, state capitals including Rio de Janeiro and Salvador had to put vaccinations on hold on Wednesday after imports of the doses were delayed.
A group representing mayors from Brazil's municipalities has asked the health minister, Eduardo Pazuello, to "urgently" resign.
"His leadership did not believe in vaccination as a way out of the crisis and did not carry out the necessary planning for the acquisition of vaccines," the group wrote on Tuesday.
Pazuello, who also faces an inquiry for his handling of an acute shortage of oxygen in the Amazon city of Manaus, did not comment.
More than 241,000 Brazilians have died from Covid-19, but President Jair Bolsonaro has repeatedly questioned the efficacy of vaccinations against the disease, dragged negotiations to import doses and essential ingredients, and said he will refuse to be vaccinated.
Fraud and misinformation have added to the problems facing local authorities. In recent days thousands of reports have emerged of people jumping the queue to receive vaccinations before priority groups while anti-vaccine disinformation campaigns have also gained traction, reaching even remote indigenous villages in the Amazon.