Greece has imposed a vaccination mandate for people aged over 60, as coverage remains below the European Union average and a recent spike in Covid-19 infections has sustained pressure on hospitals.
Older people failing to get vaccinated will face penalties, starting at a €50 fine in January and followed by a monthly fine of €100 after that.
About two-thirds of Greece's 10.7 million population are currently fully vaccinated - the EU average is just over 70%.
The rate of death and daily hospital admissions has increased following the recent spread of the Omicron variant, though pressure on ICU capacity has eased slightly.
Health minister Thanos Plevris said fines would be collected through the tax office with the money to be used to help fund state hospitals.
"The age factor is important because of its impact on the public health service," Mr Plevris told private Open TV.
A vaccination mandate was imposed for healthcare workers last year.
And starting on February 1, vaccination certificates for adults will expire after seven months unless the holder receives a booster shot.
New infections sharply surged in early January, and have eased over the past week.
The mandate for over-60s was announced in late December and, according to government data, some 41.5% of the 530,000 people targeted by the measure are now fully vaccinated.
Greece has the seventh oldest population in the world, as measured by share of residents aged 65 and over, according to the US-based Population Reference Bureau.
