MADRID: The number of Madrid residents rejecting AstraZeneca's COVID-19 vaccine has risen sharply since Spain limited its use in people under 60 in response to concerns over adverse reactions, the regional public health chief said on Friday.

Spain introduced the restriction on Wednesday after the European Medicines Agency reported a link between the shots and a rare form of brain blood clots affecting roughly one in every 100,000 people under 60 vaccinated.

The following day just 10,800 Madrid residents turned up to get an AstraZeneca injection out of more than 29,000 appointments scheduled, Antonio Zapatero told a news conference, implying a rejection rate of around 63%.

As of Thursday night, only around 45% of people had confirmed their vaccine appointments for Friday, he added.

Prior to the change in guidance, the rejection rate was around 2%.

Zapatero blamed the national health ministry, which had previously been administering the drug to key workers aged over 18, for sowing confusion and putting people off the shot.

Nevertheless, long queues formed outside the city's Wizink sports arena, now converted into a mass vaccination centre.

"This is phenomenal," said Pilar, a retired nurse hired to help out with the inoculation drive. "The more we administer vaccines, the sooner we can return to normality."

Spain aims to have around half its population of 47 million fully immunised by late July. So far around 6.4% have received a full course of two shots.