A UK study has found that the Pfizer and AstraZeneca vaccines are highly effective against the variant first identified in India after two doses.

However, the study by Public Health England found that both vaccines are less effective against the B1617.2 strain three weeks after the first dose.

The HSE says the interval between doses of AstraZeneca is to be reduced from 16 to 12 weeks but it may take some time for the second doses to be rescheduled.

And it said that any further reduction of time between doses would be a matter for the National Immunisation Advisory Committee (NIAC).

On Friday, the Chief Medical Officer described the variant first identified in India as a "black cloud on the horizon" because of suggestions that it could reduce the effectiveness of vaccines.

But the new study found that the Pfizer-BioNTech vaccine is 88% effective against the Indian variant and AstraZeneca is 60% effective two weeks after the second dose is given.

However, three weeks after the first dose both vaccines are only 33% effective.

England's Deputy Chief Medical Officer, Dr Jenny Harris, said the study was the first real world evidence of vaccine effectiveness and it showed the vaccines were just as effective after two doses as they were against the so-called Kent variant.

But a consultant microbiologist here said the results of the study should be treated with caution.

Dr Anna-Rose Prior of Tallaght University Hospital said the data also suggest that the Indian variant is more transmissible, and as it is still not clear what the trajectory of this variant is, it still remains important to prevent the spread of the variant in the first place.

In the UK, the gap between vaccine doses has been reduced from 12 to eight weeks for the over-50s and the medically vulnerable.

Earlier this week, the HSE confirmed that the interval between doses of AstraZeneca will be reduced from 16 to 12 weeks.

Today it clarified that this would apply for all of those who have received their first dose but that it may take time to reschedule second doses.

And it said that any further reduction of time between doses would be a matter for NIAC.

All of this comes ahead of a Government decision this week on the resumption of international travel.

The CEO of Tourism Ireland Niall Gibbons said news on the effectiveness of the vaccine was welcome and put hope on the horizon that a roadmap for the industry could be provided.

He said tourism needed to be reopened in a safe manner and the next four to six weeks were critical for the industry.

This latest data on the Indian variant will be a key factor in the Government's approach to foreign travel, which it has promised to clarify by Friday.

To date, there have been 72 cases in Ireland.

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Dr Jamie Lopez Bernal, consultant medical epidemiologist at Public Health England and the study's lead author, said there was more confidence in the data from the first vaccine dose compared with that from the second.

"There are bigger numbers that have been vaccinated with one dose. So I think we classify that as moderate certainty around the first dose, but low levels of confidence around the second dose."

However, Professor Susan Hopkins, PHE's Covid-19 strategic response director, said the data trend was "quite clear" and was heading in the "right direction".

PHE said the difference in the effectiveness between the vaccines may be due to the AstraZeneca second dose being rolled out later than the Pfizer vaccine.

Data also shows it takes longer for the AstraZeneca jab to reach maximum effectiveness.

There are insufficient cases and follow-up periods to estimate vaccine effectiveness against severe outcomes from the Indian variant but this will be evaluated over the coming weeks, PHE added.

Matt Hancock described the study as 'groundbreaking'

Asked about how the data could affect the UK's easing of restrictions from 21 June, Prof Hopkins said it was "too early to say".

She said: "One week post the last restriction lifting, we will be monitoring it very carefully."

Mr Hancock said: "This new evidence is groundbreaking and proves just how valuable our Covid-19 vaccination programme is in protecting the people we love.

"We can now be confident that over 20 million people - more than one in three - have significant protection against this new variant, and that number is growing by the hundreds of thousands every single day as more and more people get that vital second dose."

Dr Mary Ramsay, head of immunisation at PHE, added: "This study provides reassurance that two doses of either vaccine offer high levels of protection against symptomatic disease from the B1617.2 variant.

"We expect the vaccines to be even more effective at preventing hospitalisation and death, so it is vital to get both doses to gain maximum protection against all existing and emerging variants."

Separate analysis by PHE indicates that the vaccination programme has so far prevented 13,000 deaths and about 39,100 hospital admissions in older people in England, up to 9 May.

Latest figures show that more than 50 million doses of a Covid-19 vaccine have now been given in England.

A total of 50,246,402 Covid-19 vaccinations took place between 8 December and 21 May, according to NHS England data, including first and second doses.