Germany's vaccine commission has approved the use of the Oxford-AstraZeneca jab in people aged over 65.
The country previously approved it for under-65s only, citing insufficient data on its effects on older people.
That led to public scepticism about its effectiveness, with some Germans spurning it and leaving many doses unused.
But German Chancellor Angela Merkel said recent studies had now provided enough data to approve it for all ages.
Announcing the commission's decision on Thursday, Health Minister Jens Spahn said the move was "good news for older people who are waiting for an injection".
"The new data also shows that the vaccine is even more effective when the first and second jabs are administered 12 weeks apart," the minister said, adding that the law would be updated to incorporate the new recommendations.
Mrs Merkel said on Wednesday that Germany would follow the UK example of stretching the interval between vaccine doses in order to offer as many people as possible an initial shot.
Various studies have shown the AstraZeneca vaccine is highly effective among the elderly.
Belgium says it will also approve the vaccine for older people, following France earlier this week.
About 5% of Germans have so far received a first vaccine shot.