Authorities in northern Germany appealed to thousands of people on Tuesday to have another shot of Covid-19 vaccine after police found that a Red Cross nurse might have injected them with a saline solution.
The nurse is suspected of injecting salt solution into people's arms instead of genuine doses at a vaccination centre in Friesland, a rural district near the North Sea coast, early in spring.
"I am totally shocked by this episode," Sven Ambrosy, a local councillor, said on Facebook as local authorities issued the call to about 8,600 residents who may have been affected.
While saline solution is harmless, most of those who were vaccinated in Germany in March and April, when the suspected switch took place, were elderly people at high risk of catching the potentially fatal disease.
Police investigator Peter Beer earlier said that based on witness statements there was "a reasonable suspicion of danger".
The motive of the nurse, who was not identified, was not clear but she had shown scepticism about vaccines in social media posts, police said.
It was not immediately clear whether the suspect was arrested or charged in the case, which broadcaster NDR reported was handed to a special unit that investigates politically motivated crimes.