Spanish health authorities say they have started giving Pfizer-BioNTech vaccine doses to participants in a government-led study involving young people who received a first dose of the AstraZeneca COVID-19 vaccine.
Researchers from Spain’s Carlos III Institute want to study the effects of mixing vaccines from different manufacturers as they look for a second dose alternative following very rare brain blood clots linked to the vaccine produced by AstraZeneca.
Experts say the risks of the British=Swedish pharmaceutical company’s vaccine are less than the clot risk healthy women face while on birth control.
A total of 400 people were given the Pfizer-BioNTech vaccine for their second dose until Thursday, Spain’s Health Ministry said Friday, while 200 other people have been recruited as part of the study’s control group.
Five major hospitals across Spain are involved, and results are expected in mid-May.
There are about 2 million people under age 60 who received a first shot of the AstraZeneca vaccine before Spanish authorities halted its use in that age group.
Individuals who received their first dose on Feb. 8 should receive a second dose by May 8, according to the vaccine manufacturer’s recommendation. Authorities say that delaying the second shot is safe.