Experts recommend that authorities re-evaluate the possibility of administering a single dose to people who have gone through the disease at the same time as possibly optimizing the available doses. The advice comes as a result of a study by MedLife researchers on a sample of 741 people. In practice, research results show that people who have previously been infected with SARS-CoV-2 develop a significantly higher titer of anti-S antibodies after the first dose of vaccination.
The sample consisted of 82% women aged 21 to 82 years and 18% men aged 20 to 79 years. Samples were analyzed 18-20 days after the first dose of vaccine and 8-12 days after the booster dose, respectively.
“In order to determine the antibody titer against COVID-19, serological tests were performed against anti-nucleocapsid IgG (qualitative test on Alinity-Abbott system) and anti-spike IgG (quantitative test on Liaison Diasorin system with approximate neutralization equivalent) samples were taken both after the first dose of vaccine and after the booster dose. 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. Specialists report that only two people in the study sample did not develop antibodies following vaccination. Regarding SARS-CoV-2 infection, the study shows that 4 of those who had not previously had the disease tested positive after the first dose of vaccine, while no one in the test group tested positive. 10-12 days after the administration of the booster “, it is specified in the MedLife communiqué.
Immune response after the first dose of vaccine, decreased in people who were not infected
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% at 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, the immune response is not expected to be very intense and prolonged. Instead, the second dose “strengthens” the memory of the 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.
On the other hand, in the case of people previously confirmed with COVID-19 infection, 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 United States 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.
The company said it would continue the study in the next 3-6 months to observe the evolution of the post-vaccination antibody titer and the early identification of when the neutralizing titer starts to decrease.
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