Germany's coronavirus vaccination campaign faces delays in several cities after temperature trackers showed about 1000 of the shots made by BioNTech and Pfizer may not have been kept cold enough during transit.
"When reading the temperature loggers that were enclosed in the cool boxes, doubts arose about the compliance with the cold chain requirements," the district of Lichtenfels in the north of Germany's largest state, Bavaria, said in a statement.
Medical staff found the temperature in one vaccine transport cool box had risen to 15 degrees, a spokesman for Lichtenfels said, above the maximum of 8C stipulated by manufacturers.
He added that his district had not received advice from BioNtech yet on how to proceed.
The regional government of Bavaria's Upper Franconia region where several affected districts are based said BioNTech cleared the vaccines late on Sunday.
"BioNTech has confirmed the quality of the vaccine shots," a spokeswoman for Upper Franconia said.
"The vaccination program can start (in our region)."
BioNtech had earlier said it was responsible for the shipment to the 25 German distribution centres and federal states and local authorities were responsible for the shipment to vaccination centres and mobile vaccination teams.
"This is where the variations in temperature occurred. We are in contact with many authorities to provide advice, however it is up to them how to proceed", a BioNTech spokeswoman said.
In a December presentation, BioNtech had said once removed from the freezer, the vaccine can be stored for up to five days at 2-8C and up to two hours at temperatures up to 30C, prior to use.
The vaccine, which uses new so-called mRNA technology, must be stored at ultra-low temperatures of about -70 degrees before being shipped to distribution centres in specially designed cool boxes filled with dry ice.
Once out of ultra-low temperature storage, the vaccine must be kept at 2C to 8C to remain effective for up to five days.
The cool boxes designed by Pfizer are fitted with GPS trackers so potential storage issues can be handled en route.
The spokesman for Lichtenfels said 1000 shots had been affected by the temperature issue and the city and districts of Coburg, Kronach, Kulmbach, Hof, Bayreuth and Wunsiedel in northern Bavaria were waiting to hear from BioNTech about whether the vaccine could still be used.
"Vaccination against the coronavirus is not about who vaccinates the fastest or who does the most doses," said Oliver Baer, district administrator in Hof.
"Safety and conscientious work for the benefit of the population have the highest priority."
The European Union launched a mass vaccination drive on Sunday with pensioners and medics lining up to get the first shots.