A study by the Carlos III Health Institute of Spain (ISCIII) investigated what happens if we combine vaccines for the coronavirus developed by different laboratories.
The study investigated the consequences of administering a Pfizer dose after having applied an AstraZeneca dose.
The trial included 676 patients of different age groups and regions of Spain who had received a single dose of AstraZeneca.
They were separated into two groups: those who received the dose immediately and those who received it after 28 days.
The results, recently presented, are those analyzed 14 days after receiving the Pfizer dose: they showed a strong immune response and mild to moderate side effects in people under 60 years of age.
In addition, the protection provided by a second Pfizer jab is even greater than if it is repeated with the same vaccine. Thus, the neutralizing antibodies that protect against SARS-CoV-2 will multiply by seven, while with two doses of the same drug, that number is only three times more protection.
Based on this data, the health authorities of different countries can determine which vaccine should be administered to those under 60 who received the first dose of AstraZeneca, a group that in the Spanish case amounts to almost two million people.
"Today's results support vaccinating patients who have received the first dose of AstraZeneca, but the decision is not up to the researchers of this study," said Jesús Antonio Frías, coordinator of the ISCIII Clinical Research Network.
