Heterologous COVID-19 Vaccination in Spain: A Case Study of Individual Autonomy in the Real World

In Spain, 1.5 million essential < 60-year-old workers were vaccinated with a first AstraZeneca vaccine dose. After assessing the cases of thrombosis with thrombocytopenia associated to this vaccine, the European Medicines Agency (EMA) supported the administration of 2 doses of the AstraZeneca vaccine with no age restrictions. Nevertheless, Spain decided not to administer the second dose of this vaccine to < 60-year-olds. The government sponsored a clinical trial (CombiVacS) to assess the immunogenicity response to a Pfizer/BioNTech vaccine dose in adults primed with the AstraZeneca vaccine. The positive results backed the Public Health Commission and the Spanish Ministry of Health to offer the Pfizer/BioNTech vaccine as the booster. Nevertheless, regional public health authorities-responsible for administering vaccines-believed that, following the EMA's decision, an AstraZeneca booster dose should be given. The public confrontation of these 2 positions forced the Spanish Health Ministry to request the signature of an informed consent form to those individuals willing to receive the AstraZeneca vaccine booster and rejecting the Pfizer/BioNTech vaccine dose. Eventually, it was decided that these essential workers could choose the vaccine but signing an informed consent form. All relevant information was posted on the Ministry of Health and regional health authorities' websites and provided to potential vaccine recipients at vaccination sites. Most individuals ($ 75%) chose the AstraZeneca vaccine: perhaps because they likely trusted the EMA more than the CombiVacS results. This unprecedented and massive exercise of individual autonomy about the choice of COVID-19 vaccines from 2 different platforms has shown that adequately informed persons can autonomously weigh their options, regardless of government decisions. Exercising individual autonomy may contribute to the success of future COVID-19 booster vaccination campaigns.