Strategy followed by the United Kingdom with more than 43 million inoculated doses, by Belgium and Denmark, a few days ago Catalonia, Madrid and Andalusia asked to delay the second dose of the COVID-19 vaccine in order to immunize more people . It would be a good idea?
Within the framework of the Immunity campaign, without unity there is no immunity organized by the biopharmaceutical company MSD and with the support of 52 entities, we wanted to ask Dr. Raúl Ortiz de Lejarazu, professor of Microbiology and scientific advisor of the Flu Center of Valladolid and Dr. Federico Martinón-Torres, head of the Pediatrics Service of the Hospital Clínico Universitario de Santiago, for his opinion on this matter.
To begin with, Raúl Ortiz de Lejarazu distinguishes three scenarios in a pandemic : the pandemic, the early post-pandemic, and the late post-pandemic. The first, in which 85% – 87% of the population has not had any contact with the virus, is where we find ourselves now. The early post-pandemic would occur when there were already a significant number of people vaccinated or who had been infected naturally and the risk of new waves was lower and the late post-pandemic would be one in which both the immunity given by the vaccine and the one caused by the infection or the mixture of both changes the epidemiology of the virus.
Returning to the current scenario, the pandemic , Ortiz de Lejarazu affirms that the most pressing issue now is to get the entire naive population (those who have not had contact with the virus) to be vaccinated because we are facing a disease that can be very serious.
The first dose of the Astrazeneca vaccine or any other approved in Europe increases immunity against the coronavirus from the third week after the puncture, reaching up to 70% . The second puncture would act as a booster that would raise immunity 15% or 20% more. Ortiz de Lejarazu emphasizes that this 70% immunity would not be lost even if you had to wait a little longer for the second dose. Research indicates that the antibodies that are generated after the first dose of the vaccine are maintained for more than three months.
In the current situation in Spain, in which the percentage of vaccinated is very low , 10% -12%, the virologist finds it interesting that the entire population receives the vaccine, even if it is one dose and later the next, to that has a certain level of immunity against the coronavirus. This is precisely the strategy that the United Kingdom has followed with Vaxzevria, as well as Belgium and Denmark. Also the Centers for Disease Control and Prevention of the United States (CDC, in its acronym in English) authorized to delay the doses with RNA vaccines up to 3 months without substantially reducing the efficacy.
Federico Martinón-Torres also sees this possibility as feasible, but “in a context of strict surveillance” and it is that a single dose already begins to protect but it is not known for how long it protects because the second dose is given before the protection time that is estimated to expire. It refers to the Janssen vaccine, in which only one dose is given for the simple reason that the tests carried out by this pharmaceutical company are based on a single prick. Janssen currently has two-dose trials underway.
As of today, April 23, 2021, the Public Health Commission maintains the decision not to delay the second dose of the COVID19 vaccine . Or put another way, the second dose of Pfizer will be given 21 days after the first puncture and Moderna at 28.
