Under 60s who got AstraZeneca as first jab will get second doses of Pfizer

Spain announced on Tuesday night it would administer the Pfizer vaccine as the second dose for those under 60 who had been given AstraZeneca as their first jab.

In a subsequent meeting on Wednesday, the Spanish government and regional authorities proposed letting people decide whether to get the Pfizer jab or a second AstraZeneca dose, following criticism from scientists.

On Friday authorities confirmed that anyone under the age of 60 who wishes to receive a second AstraZeneca dose will be allowed to do so as long as they sign an informed consent form. 

The health public committee made the first decision on Tuesday evening after spending six weeks considering the issue ever since it decided on April 7 against using the AstraZeneca vaccine on people under the age of 60.

Back then, health minister Carolina Darias said two options were on the table: not vaccinating again those under 60 with one dose, or using another brand for the second dose.

Health authorities opted for the latter based on a study by Carlos III institute (ISCIII) ruling out major adverse effects when combining the brands.  

The decision also took into account research conducted in the Univesity of Oxford on the matter, and also the fact that other European countries, such as Germany, France, Portugal, Switzerland and Finland have also decided to combine jabs of different companies.

Carlos III institute study

The study from Madrid's Carlos III institute, called CombivacS, is a phase 2 clinical trial that monitored the possible effects of giving the Pfizer vaccine as the second dose to people who already received the AstraZeneca one.

673 people took part in the trial, of which 441 were administered the jab. Around 98% of them experienced only light or moderate adverse symptoms, with none of them having to be hospitalized after receiving the dose. Side effects were similar to those experienced in the standard Covid-19 vaccination patterns.

The antibody titres multiplied by 123 on average in the following 7 days and by 150 in the following 14 days.

Some scientists against decision

Some well-known Catalan scientists have criticized the move which is expected to affect 200,000 people in Catalonia.

Experts such as Daniel Prieto-Alhambra, working for the University of Oxford, called it "nonsense" because the findings of the Carlos III institute are based only on 600 people.

The fact that the combination of vaccines generates antibodies is not enough for him, because this does not necessarily mean that it is "effective" and "safe."

"Why were millions of dollars misused in doing phase 3 studies with 20, 30, or 40,000 patients, then?" he asked.

"The decision has no scientific logic. The way it has been designed, the study cannot have the conclusions they have stated," said another scientist, Salvador Macip. "Giving the second dose of AstraZeneca is safe, and the rest, we do not know yet," he tweeted, explaining that the UK is administering both doses of AstraZeneca.

Another Catalan top researcher, Oriol Mitjà, is also against the latest decision by the Spanish health authorities. "We know that the second dose of AstraZeneca is almost always safe (one thrombosis per 1,000,000 cases), while we do not know hardly anything about combining vaccines."

90,000 appointments at risk of cancelation

The Catalan health minister Alba Vergés has warned that about 90,000 appointments for people due to receive the first Pfizer dose may have to be canceled in the coming days if the decision from the Spanish health ministry is confirmed.

Vergés said this was an "unfortunate episode" in Spain's management of the AstraZeneca vaccine, which she claimed damaged confidence in the vaccine rollout among members of the public.

She reiterated the Catalan government's position, which is to administer second doses of the AstraZeneca vaccine to those who have received the first one because it has been shown that "it is safe."