Germany’s vaccine committee has said AstraZeneca’s Covid jab should only be given to people aged under 65.
The committed cited “insufficient data” over its efficacy for older people.
The European Medicines Agency is to decide on Friday whether to approve the vaccine for use across the EU.
The UK has been using the AstraZeneca vaccine in its mass immunisation programme for weeks now, and public health officials says it is safe and provides “high levels of protection”.
The German announcement follows the EU having a dispute with leading manufacturers over a shortage of vaccines on the continent.
UK-based AstraZeneca has said production issues at its Europe-based plants mean it will be unable to deliver the promised number of doses to the bloc.
However, the EU says the firm must honour its commitments and deliver the jabs by diverting stock from the UK. It is calling on members to “make use of all legal means” to secure the supply.
Pfizer-BioNTech has also cut the number of doses it is delivering to the 27-member bloc.
The independent vaccine commission advising the German government said there were “currently insufficient data available to assess the vaccine efficacy from 65 years of age” and recommended “the AstraZeneca vaccine… should only be offered to people aged 18-64 years at each stage”.
But Head of Immunisations at Public Health England, Dr Mary Ramsay said both the AstraZeneca and Pfizer-BioNTech vaccines are “safe and provide high levels of protection against Covid-19.
“There were too few cases in older people in the AstraZeneca trials to observe precise levels of protection in this group, but data on immune responses were very reassuring.”