The vaccines that will come to Spain, explained one by one

When our turn comes, they will not all give us the same vaccine. Those from Pfizer and Moderna have already arrived. The next will be AstraZeneca. 

The European Commission coordinates and negotiates the purchase of vaccines. Pfizer and Moderna have already arrived in Spain and Aragon. And the next will be that of AstraZeneca, developed at the University of Oxford, once it is approved by the European Medicines Agency, probably in February. Afterwards, explains Ignacio Aguiló, coordinator of the immunity team for the tuberculosis vaccine developed by the University of Zaragoza, "Curevac is expected, which is an RNA vaccine similar to those of Pfizer and Moderna; that of Johnson and Johnson, which is an adenovirus viral vector, similar to that of AstraZeneca, although designed to give one dose instead of two; and Novavax, which is the S protein directly together with an adjuvant, and none of these three are yet accepted. vaccines has presented efficacy data so there are still a few months before we see them"

Pfizer, Moderna and Curevac: novel RNA technology
It was thought that the first vaccines to arrive would not be the most effective, "but it has turned out that the first ones to arrive, the RNA ones, have been," says Ignacio Aguiló. "It will be another thing to see in the future how long the protection lasts, but this is something that today cannot be known, neither with RNA nor with any, because more time needs to pass."

The Pfizer and Moderna vaccines are based on novel technology. They use messenger RNA, which is introduced into human cells so that the body itself produces viral proteins that help it generate the antibodies it needs to defend itself. However, each vaccine uses its own type of lipid coating to protect the messenger RNA. Both vaccines have efficacy close to 95% and need to be administered twice (21 days apart for Pfizer and 28 days for Moderna).

Temperature is a problem for the distribution of these vaccines, "but it is difficult to change given that RNA is a very weak molecule that degrades very quickly with temperature." While Pfizer's requires temperatures between -60 and -80ºC, which has forced the organization of an expensive and complex distribution and storage system, Moderna's only requires -20ºC, like a domestic freezer. Outside of the superfreezers that the Pfizer vaccine needs, the serum lasts 5 days in a refrigerator, while the Moderna vaccine lasts up to 30 days. "The counterpart is that Moderna's can only be moved frozen at -20ºC and Pfizer's can be distributed thawed," says Luis Gascón, head of the Prevention and Health Promotion service of the General Directorate of Public Health of the Government of Aragon. and responsible for the vaccination campaign against covid in Aragon. "They will not be able to reach many countries due to lack of freezers," says Aguiló. And another disadvantage is the price: they are much more expensive than the others.