The UK will begin its autumn COVID-19 vaccination campaign in the coming weeks after authorizing booster shots made by Pfizer and Moderna that have been modified to target both the original virus and the widely circulating Omicron variant.

The country's Medicines and Healthcare products Regulatory Agency said Saturday that it had approved an updated Pfizer vaccine for used in people age 12 and older after finding it was both safe and effective. The agency authorized Moderna's updated vaccine last month.

The government will offer the vaccine to everyone age 50 and over, as well as front-line health care workers and other groups considered to be particularly at risk of serious illness as the National Health Service (NHS) prepares for a surge in infections this winter.

"These innovative vaccines will broaden immunity and strengthen our defenses against what remains a life-threatening virus," Health Secretary Steve Barclay said in a statement. "If eligible, please come forward for a booster jab as soon as you are contacted by the NHS."

Previous COVID-19 vaccines targeted the initial strain, even as mutants emerged. In the new "bivalent" boosters, half of the shot targets the original vaccine and half offers protection against the newest Omicron variants.