Chile has one of the world's highest vaccination rates with around 75% of its 15 million residents have already received at least one dose of vaccine. Nearly 58% are fully inoculated.
Despite the mass vaccination drive, Covid cases in Chile have surged 17% in the past two weeks across the country, and 25% in the Santiago metropolitan region that is home to half the country's population.
Intensive care beds in the capital region are now at 98% capacity.
Vaccines are not 100% effective and there is a time delay before they reach their highest efficacy.
Chile's second wave has also been driven by lockdown fatigue and the more contagious Brazil or Gamma (P1) variant.
Of 7,716 the Covid cases reported in Chile between Wednesday and Thursday, 73% had not been fully inoculated and 74% were under 49 years old, the health ministry said.
Dr Cesar Cortes, emergency physician at the University of Chile hospital, said without its vaccines, Chile would be far worse off.
"The complicated situation we are seeing now would be catastrophic," he said.
The step comes as the UK government considers a delay to the June 21 so-called "freedom day" in England amid a surge in cases fuelled by the Delta variant, which now makes up 91% of cases of coronavirus in the UK.
More than 77.6% of the adult population in the UK has received at least once dose of a Covid vaccine.
Government data up to the end of Wednesday, June 9 shows that of the 69,743,980 jabs given in the UK so far, 40,886,878 were first doses – a rise of 176,559 on the previous day.
Some 28,857,102 were second doses, an increase of 316,258.
The number of Covid-19 patients in hospital in England stood at 906 as of 8am on Thursday, June 10, according to the latest figures from NHS England, up from 779 a week earlier and is the highest number since May 12.
Boris Johnson said on Wednesday: "I think what everybody can see very clearly is that cases are going up and in some cases hospitalisations are going up and I think what we need to assess is the extent to which the vaccine rollout, which has been phenomenal, has built up enough protection in the population in order for us to go ahead to the next stage."
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