MADRID — The vaccination roll out in Spain has slowed down with most activity halted over the New Year and Epiphany holidays until after Jan. 6.

Reports from regional authorities showed that less than one-fifth of the existing doses of the Pfizer-BioNTech vaccine had been administered by Monday, just as the country is set to receive a new batch of 350,000 doses..

Some experts fear that further delays could hamper the authorities’ ability to safely store the vaccines, which need to be kept at extreme low temperatures.

Some regions are blaming the delays on a shortage of nurses and other medical personnel over the holiday period.

Authorities in the northeastern Catalonia region are also blaming the delays on a shortage of freezers to store the vaccine, after a batch was caught up in a bottleneck of trucks trying to enter the European mainland from the U.K.

Preliminary data reported by some Spanish regions show that contagion for the new virus has been on a steady increase in recent days. Spain this week is set to surpass 2 million confirmed coronavirus cases and more than 50,000 deaths.