Not all people develop the same immune response to the vaccine. As with all medications, not all people respond in the same way to them. In addition, it must be taken into account that the currently circulating strains that most predominate are Delta and Lambda, “more infectious and resistant to vaccines”.
“In this way, we move away from that figure of 70% of the vaccinated population that was initially thought necessary to achieve the desired herd immunity , making it necessary to reach a higher number of vaccinated to be able to speak of group immunity” , explains Dr. Antonio Moreno Villena, a doctor assigned to the R + D + i Area of Quirónprevention , a company for the prevention of occupational risks of the Quirónsalud group .
Of course, this expert celebrates that, according to the latest data registered and shared by the Ministry of Health , there are already more than 35 million Spaniards vaccinated and with the complete guideline against Covid-19 , that is, more than 73.5 % of the population , “a very positive percentage compared to other European countries that are further behind.”
Indeed, one of the great doubts that surrounds vaccination against SARS-CoV-2 infection is how long the protection conferred by these injections lasts. Moreno Villena recognizes in this sense that “it is known and the laboratories themselves have recognized it”, that after the inoculation of the vaccine there is a loss of immunity over time.
In fact, remember that the Ministry of Health itself collects in its Information document on immunity against Covid-19 that, for example, the efficacy of Moderna’s vaccine , from day 14 after the second dose, reached 95 6% for those between 18 and 64 years old and 86.4% for those of older age; while the efficacy between days 14 and 28 was 92.1%; In addition, in the risk groups for severe Covid-19 it was 90.9% and 94.4% for all ages and for those between 18 and 64 years, respectively.
Regarding the Pfizer formula , he points out that Health indicates that its effectiveness seven days after the second dose was 95%, and similar in those under or over 55 years of age; in those with baseline pathology, it reached 95.4%.
“In relation to the efficacy depending on the number of doses and the elapsed time was 86.7% for those who received the vaccine ≥10 days after the first dose and up to the second and 90.5% on day 7 after the reception of the second dose. This is a trend that can be extrapolated to other vaccines and that raises the debate about whether a third dose or ‘booster dose’ will be necessary ”, emphasizes the expert from Chironprevention.
Related to the above, the specialist also draws attention to seroconversion, a phenomenon that takes place in our body after vaccination: “After three weeks of having received the last dose of the vaccine that has been inoculated (a single dose if it is the Janssen vaccine) should produce a seroconversion in our body , being able to detect, through a serological test, how much specific antibodies against the Covid-19 virus we have “.
However, it specifies that this will vary depending on the efficacy of each vaccine and the time that has elapsed since vaccination, as well as other factors that in certain cases may compromise the immune response or its quality (following certain pharmacological treatments, advanced age , etc).
“Generating antibodies (be they neutralizing or just protective) is already a success”
“By setting ourselves a post-vaccination scenario of 100% vaccinated, are our problems over? Well, unfortunately it turns out not. Because not all people develop the same immune response to the vaccine. In addition, it must be clarified that the presence of antibodies does not guarantee that we are protected against infection. For that we should generate neutralizing antibodies and at the moment we only have data on the amount of antibodies, not on their ability to dismantle the virus. Of course, generating antibodies (whether neutralizing or just protective) is already a success ”, warns the doctor assigned to the R + D + i Area of Quirónprevention.
Moreover, it highlights that 5-10% of vaccinated cases will not seroconversion occur because the body does not generate antibodies. Here, Dr. Antonio Moreno Villena points out what the UITB Foundation collects in his document ‘Review of vaccines against SARS-CoV-2’: “Given that the efficacy in clinical trials is around 90%, if at the community, if this same percentage of vaccine effectiveness is observed, coverage should be increased assuming that there is a percentage of vaccinated, around 10%, who are not immunized ”.
The importance of serological tests
For all these reasons, the Quirónsalud expert considers it convenient to carry out diagnostic tests for COVID-19, “an indispensable control tool for countries, institutions and companies” , despite the fact that we achieve a percentage of vaccinated that grants us the title of immunity group.
“Although the percentage of people who do not develop a sufficient immune response after the vaccine will be low, between 5 and 10%, it is a problem of both public health and prevention of occupational risks, which is what Quirónprevention is responsible for. How should a company act to know the immunity of its employees? How to deal with a number of people who do not have immunity against the virus? What tools should companies have to know, control, and take care of the health of their workers in the post-vaccination phase? ”, The expert wonders.
More specifically, he believes that it will be the serological test that will be able to provide relevant information on the immune response and will help in this regard: “ The ideal is to plan an immunity study with periodic tests that can provide us with information on the initial immunity and its evolution over time. the long of the time. This can give us clues as to whether or not we will need a booster dose and which subpopulation of workers are subsidiary to receiving it, in accordance with the criteria established by Health ”.