Only 32 people were admitted to hospitals in the UK with Covid-19 after they were vaccinated, real-world data reflecting the effectiveness of vaccines showed.
The preliminary figure, from the UK Coronavirus Clinical Characterisation Consortium, represents a tiny fraction of more than 74,000 people admitted to hospital with coronavirus during the period studied.
A separate Financial Times analysis shows infection rates, hospital admissions and deaths have fallen across all age groups in the UK.
The data shows all three measures have fallen further and faster among the elderly, who were prioritised for vaccines under the government's staggered distribution strategy.
Former prime minister Tony Blair is pressuring the government to release comprehensive data on the vaccination programme to restore worldwide confidence in the vaccine developed by Oxford-AstraZeneca, which is being linked to rare but serious blood clots.
Mr Blair on Wednesday said it was crazy for medicines regulators to restrict the use of a highly effective vaccine.
"The UK is probably the only country in the world where millions and millions of people have had both Pfizer, the mRNA vaccine, and AstraZeneca, an adenovirus vaccine, and therefore a comparison between the two would be extremely powerful," he told the BBC Radio 4 Today programme.
“You’ve now got a crazy situation where you have regulators – not just in Europe, but countries in Africa refusing the AstraZeneca vaccine – when it will have a huge and beneficial impact on their people.”
He suggested the release of data that would show how many people had contracted Covid-19 and subsequently died from the disease after receiving the vaccine.
“If you do that it will show that AstraZeneca is a highly effective vaccine and those doubts that are there are unjustified and wrong,” Mr Blair said.
"The reason why we need AstraZeneca to have that credibility is because AstraZeneca – along with Johnson & Johnson, the two big adenovirus vaccines – are going to be the workhorse vaccines for vaccinating the world."
Detailed figures showing hospital admissions among those who received the shot will be handed to government ministers this week.
The research showed that less than 2,000 people who received the vaccine were admitted to hospital among 74,405 Covid cases referred for clinical care between September and March. There were only 32 people admitted to hospital three weeks after receiving the injection, when immunity kicks in.
Prof Calum Semple from the University of Liverpool said the findings gave him confidence in the government’s road map out of lockdown.
"When you come away from clinical trials we can still show that the vaccine is working in the real world," he said.
"What this means is provided we get the vaccination rollout then I can see no reason why the road map isn’t adhered to."
He said the severity of another Covid outbreak later in the year would depend on how many people were still unvaccinated.
"The problem is if further sections of society choose not to be vaccinated and then we get a second outbreak, perhaps later in the summer, which is what has been predicted," he said.
The UK hit a milestone on Tuesday with more than 10 million people inoculated with both doses of a Covid-19 vaccine.
Separate data published by Public Health England suggested one dose of a vaccine developed by either Pfizer or AstraZeneca prevented about four in five hospital admissions among over-80s.
Death rates in steep decline in vaccinated older people
According to Office for National Statistics figures, the death rate has plummeted across all age groups.
A dramatic decline in the death rate was seen to take effect in older, more vulnerable people after 50 per cent of over-80s received their first dose of a Covid-19 vaccine on January 25.
Prime Minister Boris Johnson said on Tuesday the vaccination campaign was saving lives but warned Covid-19 still remained a threat.
“We know that this vaccination programme is making a big difference. We know it’s helping to reduce suffering and save lives, potentially on a very big scale,” he said.
“But we don’t yet know the full extent of the protection we are building up, the exact strength of our defences. And as we look at what is happening in other countries with cases at record numbers around the world, we cannot delude ourselves that Covid has gone away.”
In another positive sign for the UK's immunisation campaign, officials said uptake of vaccines among ethnic groups had tripled since February.
Vaccine uptake success in ethnic groups
Dr Nikita Kanani, medical director of primary care for NHS England, said "significant progress" had been made in convincing minority groups to take the shot.
Data shows that uptake increased from 1.89 million as of February 7 to 5.78 million on April 7 for all minority ethnic groups.
Uptake among people from Bangladesh rose five-fold from 29,382 to 152,408 over the same period, while it increased four-fold among Pakistani groups, from 88,956 to 367,780.
The data also estimates that 61.6 per cent of people of black Caribbean ethnicity aged 50 and over had received a first dose as of April 7 – the lowest proportion of all ethnic groups.
Dr Kanani said the achievement “feels really personal to me both as a GP and as a woman of colour”.
“The progress is a direct result of a combination of NHS teams who know and understand their communities, community and faith leaders who’ve worked really closely with us, practical considerations about Ramadan and other local nuances, and really strong vocal backing from high-profile people," she said.
“So I want to thank everyone involved in this effort. You’ve saved lives.”
With cases in retreat in the UK, Swiss pharmaceutical company Roche said on Wednesday it was looking for another location to test its Covid-19 pill as it was too difficult to find patients.
Bill Anderson, head of Roche's pharmaceutical division, said the swift vaccination programme and strict lockdown meant it was taking longer than expected to collect trial data in Britain.
"There are just simply not enough patients to enrol ... with the speed we were hoping for," he said.
"That's been one of the challenges since the beginning of the pandemic: you set up sites where there's a lot of Covid, and then by the time you're ready to enrol, the pandemic has moved somewhere else and you're sort of chasing it."
EU vaccine drive gathers pace
Meanwhile, the EU's long-awaited Covid-19 shot surge is finally here, raising hopes the continent can bring the pandemic under control and reopen economies faster than expected.
Germany has nearly doubled the pace of vaccinations after an increase in supplies and the decision to let general practitioners administer doses in their regular offices. France, Italy and Spain are following a similar trajectory.
The improvement in the pace of inoculations is a welcome development for EU governments after a first quarter marked by a stuttering campaign that left the bloc lagging behind the UK and the US. The continent was also hit with a fresh wave of the virus, pushing countries to reintroduce strict lockdown measures.
Prof Martin McKee from the London School of Hygiene and Tropical Medicine said continued success should see the continent get past the open-and-close cycle of lockdowns.
“This is a reminder of the importance of looking beyond the headline comparisons to understand the dynamics,” he said
“The real challenge will be how to maintain momentum as we get to relatively high coverage rates, especially if, when cases fall over the summer, people become complacent.”