LONDON — The UK said on Tuesday that it will offer a third dose of coronavirus vaccine to everyone over 50 and other vulnerable people to help the country ride out the pandemic through the winter months.

The booster shots, which will be rolled out beginning next week, were approved a day after the Conservative government also backed plans to offer one vaccine dose to children 12 to 15 years old.

The announcement came on the day Boris Johnson set out the government's plan for tackling COVID-19 over the autumn and winter months in England. Scotland, Wales and Northern Ireland confirmed they are to make similar moves.

Speaking from a news conference in Downing Street, the prime minister called the UK's COVID-19 situation "actually more challenging" than it had been a year ago.

The government advisory body, the Joint Committee on Vaccination and Immunization (JCVI), recommended that booster shots be offered to everyone over 50, health care workers, people with underlying health conditions and those who live with people whose immune systems are compromised. They will be given no earlier than six months after a person received their second dose of vaccine.

Around 30 million people will be eligible for the booster shots, which aim to protect against a modest waning in immunity among those who have received two jabs.

The JCVI said the Pfizer vaccine should be the primary choice for booster shots, with a half-dose of Moderna as an alternative.

The decision to offer booster shots is not one that's being recommended by the World Health Organization, which has asked wealthy nations to delay giving them out until every country has vaccinated at least 40% of their people. Only a few other wealthy countries have recommended their use.

England's chief medical officer, Chris Whitty, said it's hugely important that developing countries get the jabs they need, saying the UK had an "absolute moral imperative" to make sure vaccines were donated. — Euro news