UK Prime Minister Boris Johnson will receive the Oxford/AstraZeneca vaccine to protect against COVID-19 on Friday, even as many European countries who had paused its use amid some blood clot fears began resuming the jabs.

The European and UK regulators said they had conducted a thorough scientific review of all the available data and concluded that the available evidence does not suggest that blood clots in veins (venous thromboembolism) are caused by the COVID-19 vaccine developed by the University of Oxford and produced by AstraZeneca, which is also being manufactured in India by the Serum Institute of India.

The UK's Medicines and Healthcare products Regulatory Agency (MHRA), however, does advice that anyone with a persistent headache beyond four days after receiving their vaccine should seek medical advice.

Our thorough and careful review, alongside the critical assessment of leading, independent scientists, shows that there is no evidence that that blood clots in veins is occurring more than would be expected in the absence of vaccination, for either vaccine, said Dr June Raine, MHRA Chief Executive.

You should therefore continue to get your jab when it is your turn. While we continue to investigate these cases, as a precautionary measure we would advise anyone with a headache that lasts for more than four days after vaccination, or bruising beyond the site of vaccination after a few days, to seek medical attention, she said.

The MHRA's investigation found a very small number of reports of an extremely rare form of blood clot in the cerebral veins (sinus vein thrombosis, or CSVT) occurring together with lowered platelets soon after vaccination. This type of blood clot can occur naturally in people who have not been vaccinated, as well as in those suffering from COVID-19.

Therefore, the health experts say that given the extremely rare rate of occurrence of these CSVT events among the 11 million people vaccinated, and as a link to the vaccine is unproven, the benefits of the vaccine in preventing COVID-19, with its associated risk of hospitalisation and death, continue to outweigh the risks of potential side effects.

However, please remember that mild flu-like symptoms remain one of the most common side effects of any COVID-19 vaccine, including headache, chills and fever.

These generally appear within a few hours and resolve within a day or two, but not everyone gets them. We will continue to robustly monitor all the data we have on this extremely rare possible side effect, added Raine.

Meanwhile, during a Downing Street briefing on Thursday evening, Boris Johnson repeated his previous assertions that both vaccines currently being administered by the National Health Service (NHS) are safe and effective.

So the Oxford jab is safe; and the Pfizer jab is safe the thing that isn't safe is catching COVID which is why it's so important that we all get our jabs as soon as our turn comes, he said.

And as it happens, I'm getting mine. And the centre where I'm getting jabbed is currently using the Oxford AstraZeneca vaccine for those receiving their first dose, and that is the one I'll be having, said the 56-year-old, who qualifies for a jab after the NHS expanded its rollout to all adults aged over-50.

The UK PM also sought to allay fears around the supply of vaccines, which has been attributed to a delay in the delivery of 5 million doses from the Serum Institute of India, a company he praised for its herculean job of manufacturing vaccines in large quantities.

Johnson said: We've always said that in a vaccination programme of this pace and this scale, some interruptions in supply are inevitable and it is true that in the short term we are receiving fewer vaccines than we had planned for a week ago.

That is because of a delay in a shipment from the Serum Institute, who are doing a herculean job in producing vaccines in such large quantities and because of a batch that we currently have in the UK that needs to be retested as part of our rigorous safety programmes. So as a result we will receive slightly fewer vaccines in April than in March. But that is still more than we received in February.

He reiterated that the supply speed would not affect the timetable set for all adults to receive their anti-COVID jabs by end-July or for the lockdown to be eased in phases over the next few months.

There is no change to the next steps of the roadmap, he said.

Meanwhile, the latest Office for National Statistics (ONS) figures suggest infection levels have continued to decrease across England and Wales but have "levelled off" in Northern Ireland and increased in Scotland. An estimated one in 335 people in the UK had COVID-19 in the week to March 13, according to the figures.

On Thursday, the UK recorded 6,303 new coronavirus cases and 95 deaths, taking its death toll from the deadly virus to 125,926.

PTI