Wales has become the second UK nation to give half of young teenagers a first dose of Covid-19 vaccine, figures show.
An estimated 50.9% of 12 to 15-year-olds had received their first jab by November 15, according to Public Health Wales.
Scotland was the first nation to give a jab to half its young teenagers, passing the milestone on October 21.
Take-up in Scotland currently stands at 56.7%.
Both nations are some way ahead of England, which has given a first dose to 36.3% of 12 to 15-year-olds, and Northern Ireland, which is on 22.9%.
The figures have been published by the four UK health agencies.
Vaccines have been rolled out to young teenagers in different ways across the UK.
First doses have been available to 12 to 15-year-olds in Scotland since September 20, and have been delivered mostly at drop-in clinics and other community settings.
The rollout in England also began on September 20, but was initially delivered mainly by NHS teams in schools.
This changed just before the half-term holiday when parents and children became able to book a jab online at a local vaccination centre.
There are signs that take-up in England has picked up pace since half-term, with coverage rising from 26.2% on November 1 to 32.2% by November 8 and 36.3% by November 15.
By contrast take-up in Scotland is slowing, with the latest figure of 56.7% up only slightly from 55.5% a week earlier.
In Wales, first doses have been available to 12 to 15-year-olds from October 4.
Most are being given at vaccination centres with a small number in schools.
In Northern Ireland, 12 to 15-year-olds have been offered the vaccine in schools since early October.
Figures are calculated slightly differently in the four nations, with England and Wales using age groups based on their national immunisation databases and Scotland and Northern Ireland using the latest official population estimates.
Take-up of first doses among 12 to 15-year-olds varies considerably across the regions of England, analysis by the PA news agency shows.
While more than four in 10 young teenagers have received a jab in the South East (44.0%) and eastern England (42.9%), the figure is just under three in 10 in London (28.4%).
Yorkshire and the Humber is on 34.0%, the West Midlands 34.4% and the North West 34.4%.
The East Midlands is at 38.8%, the North East 38.3% and the South West 35.0%.