The fourth dose will also be given to healthcare professionals, nursing home staff and residents, and to anyone 5 years and older with health conditions that make them more vulnerable to serious illness from COVID-19.
Most of the same groups also get a free flu shot.
British Prime Minister Boris Johnson said the booster campaign would “keep our defenses strong through the autumn and winter”.
“Vaccines were our way out of this pandemic, and now they will ensure that COVID can never haunt us in the same way again,” he said.
Like many European countries, Britain is experiencing an increase in COVID-19 cases, driven by the ultra-infectious BA.4 and BA.5 subvariants of the omicron strain. The Office for National Statistics estimates that 1 in 19 people in England had the virus in the week ending July 6.
The UK has one of Europe’s highest official death tolls during the pandemic, with nearly 178,000 confirmed deaths of people who tested positive.
Follow all AP stories about the pandemic at https://apnews.com/hub/coronavirus-pandemic.