Post-Vaccine Immunization Study: People who have not been infected with SARS-CoV-2 develop fewer anti-Spike antibodies than those who became infected and were vaccinated with the first dose – Essential


MedLife announces new findings in the first post-vaccination immunization study. Because the immune response after the first dose of vaccine is low in people who have not previously had the disease, MedLife recommends that authorities carefully re-evaluate the possibility of a single dose for people who have had the disease at the same time as optimizing the available doses.

• The MedLife Group’s research division expanded the sample from 179 people initially enrolled in the study to 741 people. Of these, 85% did not undergo SARS-CoV-2 infection.
• Only two people in the evaluated sample did not develop antibodies after vaccination, respectively 0.27%.
• 4 people in the category who did not have COVID-19 infection in the past tested positive after receiving the first dose of vaccine.
• No person in the analyzed group tested positive 10 to 12 days after the booster dose.
• All individuals who have previously experienced the disease have developed a significant titer of neutralizing anti-Spike antibodies after administration of the vaccine.

The samples analyzed by the specialists of the research division of the MedLife Group come from a sample of 741 people, in proportion of 82% from women aged between 21 and 82 years and from 18% from men aged between 20 and 79 for years. In order to dynamically observe the evolution of the antibody titer, the samples were analyzed within 18-20 days after the administration of the first dose of vaccine and, respectively, at 8-12 days after the administration of the booster.

In order to determine the antibody titer against COVID-19, serological tests were performed against IgG anti-Nucleocapsida (qualitative test on Alinity-Abbott system) and IgG anti-Spike (quantitative test on Liaison Diasorin system with approximate equivalence in neutralization titer), samples being harvested both after the first dose of vaccine and after administration of the booster.

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From the analyzed sample, two categories were highlighted: 85% are people without a history of COVID-19 infection in the past, while 15% have previously gone through the disease, having confirmed the infection by RT-PCR test performed previously. The specialists announce that only 2 people from the studied sample did not develop antibodies following the vaccination. Regarding SARS-CoV-2 infection, the study shows that 4 people who had not previously had the disease tested positive after the first dose of vaccine, while no person in the test group tested positive. 10-12 days after administration of the booster.

The immune response after the first dose of vaccine is low in people who have not been through the disease before

Analysis of samples from people who have not been infected with the SARS-CoV-2 virus in the past shows that the immune response remains low before the booster, given that 48% of those who received the first dose did not develop anti-Spike antibodies. IgG in a concentration greater than> = 80AU / ML within 18-20 days of vaccine administration. At the same time, the specialists also identified a person who did not develop any antibodies during this period. In contrast, it has been observed that the percentage of people who have developed anti-Spike IgG antibodies at a concentration> = 80AU / ml, although they have not previously experienced the disease, increases considerably, to 99.5%, 8-12 days after administration of the second dose. However, there is one person who has not developed antibodies in this booster interval either.

“The three vaccines currently being administered in Romania are not identical in structure as an antigenic determinant, but all three will sensitize immune cells and generate anti-S (Spike) antibodies. At the first dose of vaccine, in an organism that has not been in contact with the SARS-CoV-2 virus, it is expected that the immune response will not be very intense and prolonged. Instead, the second dose comes to “strengthen” the memory of antibody-producing cells, so that the immune response is long-lasting and strong enough to neutralize a future viral infection, “said Dr. Bogdan Dabu, chief laboratory physician. within MedLife.

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People who have previously been infected with SARS-CoV-2 develop significantly higher anti-S antibody titers after the first dose of vaccination

On the other hand, in the case of people previously confirmed with COVID-19 infection, MedLife specialists point out that the titer of neutralizing antibodies is significant, from the first days after the administration of the first dose of vaccine. This reinforces the hypothesis launched by other groups of researchers in Europe and the US that a single dose of vaccine could be effective for people who have gone through the disease. In fact, on the sample studied by MedLife specialists, all people who had previously undergone the infection had developed a high titer of neutralizing antibodies within 18-20 days of the first dose.

“Following infection with SARS-CoV-2, both anti-N and S-antibodies can be detected, these being a specific marker of the” meeting “between the virus and the host organism. However, what draws our attention is the titer of anti-S antibodies developed after vaccination by people who have gone through the disease compared to those who have not come into contact with the virus until the time of vaccination. Thus, we notice that those in the first category can develop, after the administration of the first dose, a significantly higher antibody titer than those who have not gone through the disease “, added Dr. Dabu.

MedLife representatives announce that the research approach continues, the objective being to monitor in the medium and long term (3, 6 months) the evolution in dynamics of the titer of antibodies acquired post-vaccination and the early identification of the moment when the titer of neutralizing antibodies begins to decreases. At the same time, the company has an extensive sequencing study of the SARS-CoV-2 genome, following the path and mutations that the virus can undergo.

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