The percentage of people who believe the AstraZeneca vaccine causes blood clots has nearly doubled since last month, but overall vaccine confidence is higher than it was at the end of 2020.

A survey of 4,896 UK adults aged 18 to 75 also found a growing proportion of the population are keen to be vaccinated as soon as possible, with the prospect of foreign holidays and vaccine passports among the reasons most commonly cited.

The research, by Bristol University, King’s College London and the NIHR Health Protection Unit, was carried out between April 1 and 16.

The Joint Committee on Vaccination and Immunisation (JCVI) issued updated guidance on April 7 stating that under-30s should be offered an alternative to the AstraZeneca vaccine as their risk of developing a blood clot was slightly higher than the benefit in terms of preventing a Covid intensive care admission when the prevalence of coronavirus in the community is low.

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For other age groups, the risk:benefit ratio continued to favour vaccination.

The survey found that 17% of those interviewed in the first week of April believed the AstraZeneca vaccine caused blood clots, compared to 31% after the advice changed.

HeraldScotland: An analysis presented by the JCVI earlier this month indicated that, when virus rates are low, the benefit of the vaccine for under-30s was slightly outweighed by the risk of serious harms - although this was at a rate of 1.1 per 100,000An analysis presented by the JCVI earlier this month indicated that, when virus rates are low, the benefit of the vaccine for under-30s was slightly outweighed by the risk of serious harms - although this was at a rate of 1.1 per 100,000

However, 81% now say vaccines are safe, compared with 73% who said the same at the end of 2020.

This include 39% who strongly agree that this is the case – up from 30%.

Vaccine enthusiasm has increased, with 46% of unvaccinated people saying they are certain to take up the jag when offered compared to 36% at the end of 2020.

One in five (18%) who had changed their minds cited "the wish to go on holiday, including the possibility of vaccine passports".

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Professor Bobby Duffy, director of the Policy Institute at King’s College London, said: “The blood clot scare has affected how some of the public view the Astra Zeneca vaccine – but has not reduced confidence in vaccines overall."

Dr Siobhan McAndrew, senior lecturer in Quantitative Social Science at Bristol University, said: “The public health challenge remains complex: to respond to the concerns and information needs of a diverse population, to support the pro-vaccine social norm, and to offer meaningful reasons to take up the vaccine to those who remain unconvinced.”