After the second dose, many have asked the same question: How long does it take for the body to generate the immunological memory that protects us from COVID-19? Once the second vaccine is given, are we immediately immunized?
At the Gregorio Marañón Hospital, researchers Rafael Correa Rocha and Marjorie Pion, from the Immuno-regulation Laboratory, have coordinated a study to answer this question based on the Pfizer/Biontech and Moderna vaccines.
With the collaboration of the Microbiology and Occupational Health Services of the Marañón, and the support of Jordi Ochando of the Carlos III Health Institute, the Immune response to the vaccine in hospital volunteers, measuring the cellular response at three, seven and fourteen days after vaccination.
“We asked ourselves this question because it had been observed that people who received the first dose, or even just received the second dose, became reinfected again.”
Rafael Correa Rocha, researcher at the Immuno-regulation Laboratory
This field work, carried out by Sergio Gil and Diego Carbonell, from the Immuno-regulation Laboratory, reflects that the maximum level of protection with the Pfizer-Biontech vaccine is not reached until seven days after receiving the second dose. In the case of the vaccine Modern the level of cellular response generated is higher than that produced by Pfizer’s, but the maximum level of protection is not reached until 14 days later to complete the vaccination schedule.
Thus, there is a period of between 7 and 14 days where immunological protection has not reached its maximum level and during this time, according to Correa, we are not protected.
Despite the fact that experts do not know at the moment what is the cellular response value from which a vaccinated individual is completely protected from infection, Correa points out that these results push them to make the population aware of the danger they run during this period.
“The fact that having received only the first dose of these vaccines is probably not enough to confer protection. Even after receiving the second dose, there is a window of 1-2 weeks where the level of protection has not yet reached its maximum.
The maximum level of protection with the Pfizer-Biontech vaccine is not reached until seven days after receiving the second dose
“For this reason,” he adds, “we must continue to take extreme precautions, especially in people who have recently been vaccinated or who have not completed the full regimen. What’s more, It should not be forgotten that these vaccines drastically reduce the risk of suffering from the disease and of developing serious symptoms., saving many lives. But nevertheless, they do not guarantee 100 percent that we cannot get infected and transmit the virus to others unvaccinated people or at higher risk, so the mask and the usual precautions remain the most effective measure to prevent the spread of the disease.
This work has been published in the journal Frontiers Immunology and signed by the four researchers from the Sanitary Research Institute of the Gregorio Marañón Hospital.
One of the lines of study in the international field focuses on know the evolution of induced immunity thanks to the vaccine. It is expected that the intense response elicited at the time of vaccination will diminish over time, but experts indicate that it is not yet known whether or not the immune memory values that persist are sufficient to prolong long-term protection. For this reason, what level of cellular response is necessary to maintain to confer protective immunity and to prevent the spread of the pandemic is being studied.
The level of cellular response generated by Moderna’s vaccine is higher than that produced by Pfizer’s, but the maximum level of protection is not reached until 14 days after completing the vaccination schedule.
Waiting for these studies, the administration of a third dose increases in any case the level of immunological memory, and will strengthen protection against the development of COVID-19, especially in those people who are more vulnerable or more exposed to infection.