FRANKFURT (AFP) - A nurse in Germany was under investigation Sunday (April 25) after she admitted to swopping the coronavirus vaccine for a saline solution in six cases because she wanted to cover up that she had dropped a vial of the Pfizer-BioNTech vaccine.

Authorities are now urgently asking 200 people who were inoculated at the German Red Cross vaccination centre in Friesland last Wednesday (April 21) to come forward to be tested for antibodies to determine which six people missed out on the vaccine.

Police in Wilhelmshaven, Friesland in northern Germany said in a statement they had opened a probe into possible "bodily harm" by the nurse, while stressing that the saline solution did not pose a health risk to those affected.

It is standard practice for the Pfizer-BioNTech vaccine to be diluted with saline before it is administered, and it was the nurse's role to prepare the jabs when she accidentally dropped one of the little bottles, wasting its contents.

She confessed her action to a colleague, who raised the alarm on Saturday.

"The woman said the reason for her action was to avoid having to inform anyone about the dropped vial," the statement said.

The local district has set up a hotline for people who were vaccinated on the day of the incident to come forward so they can be tested.

"I am deeply shocked by the incident," said Friesland district administrator Sven Ambrosy, adding that authorities have now introduced a "four eyes" procedure at the vaccination centre to make sure no one is left alone with the vials.