London(CNN) All adults in the United Kingdom will be able to get their booster Covid-19 vaccine doses three months after their second shot, the government indicated on Monday, in a dramatic acceleration of the country's inoculation drive that comes amid fears over the Omicron variant.
Boosters had previously only been available a minimum of six months after a second dose, for people over 40 and for over-16s with underlying health conditions.
By slashing the gap to a minimum of three months, the UK will soon offer one of the smallest intervals of any country in the world.
Health Secretary Sajid Javid confirmed he had accepted the move in Parliament on Monday, hours after the UK's advisory body on vaccinations recommended it. England is also reinstating a mask mandate in shops and on transport from Tuesday, a move announced over the weekend that was also sparked by concerns about Omicron.
The new step will heighten concerns about geographic inequalities in the effort to protect people from Covid-19 -- a disparity which was highlighted since the concerning new variant was discovered in southern Africa, where vaccination rates are lower.
"We've always known that a worrying new variant could be a threat to the progress that we've made as a nation," Javid told lawmakers.
"We're learning more about this new variant all the time, but the latest indication is that it spreads very rapidly," he said, adding that there is "a reasonable chance that our current vaccines may be impacted."
The UK has so far administered 17 million booster shots, inoculating 31% of its over-12 population, according to official data.
The expansion of the rollout means tens of millions are now eligible, far sooner than they initially would have been, and puts the country once again in a position separate from most nations when it comes to vaccines.
Most other countries deploying boosters have invited people for a third shot six months after their second dose. The UK previously broke the mold with its initial rollout in January, when it offered first and second doses 12 weeks apart in an effort to get more people some level of protection sooner.
The prospect of a new variant emerging in a part of the world where vaccination coverage is lower has been warned about for months, and led to some calls for richer countries to prioritize donating surplus doses, rather than kickstarting their booster rollouts.
According to the World Health Organization (WHO), only 7.5% of people in low-income countries have received at least one dose of the coronavirus vaccine. Across the eight countries most affected by the travel bans related to the Omicron variant, the proportion of populations that have had at least one vaccine dose ranges from 5.6% in Malawi to 37% in Botswana.
Labour's shadow health minister, Rosena Allin-Khan, told Javid in Parliament that "this variant is a wake-up call" and that "no one is safe until all of us are safe." She criticized Prime Minister Boris Johnson's government for its lack of mitigation measures and for not pressing to send doses to poorer nations.
But Javid said Allin-Khan had "misjudged the tone" of the debate, adding: "Surely she isn't blaming the UK's government for the emergence of this new variant."
Michael Head, a senior research fellow in global health at the University of Southampton, told CNN on Sunday the emergence of new variants was "a natural consequence of being too slow to vaccinate the world."
"We still have large unvaccinated populations, like we have across sub-Saharan Africa, and these are susceptible to big outbreaks," he said.