The Northwestern University study stressed the importance of receiving a second dose of the Corona vaccine, not only because it is generally known that immunity from vaccines diminishes over time, but also because of the risks posed by emerging variables, including the highly contagious delta variant..
According to a report by the Times of India, the study also showed that prior exposure to the Corona virus does not guarantee a high level of antibodies, nor does it guarantee a strong antibody response to the first vaccine dose..
This directly contradicts the assumption that infection with corona will make a person naturally immune to re-infection, as the results also support vaccination (two doses) even for people who have had the virus previously..
A team of scientists, including biological anthropologist Thomas McDade and pharmacologist Alexis Demonbreun By testing blood samples from adults who tested positive for the coronavirus to measure how long the immune benefits of the Pfizer and Moderna vaccines last and how well they protect against new variants, study participants were selected from a diverse community sample of Chicago-area adults who were recruited at the start of the epidemic..
Using in-house lab-developed antibody test kits, participants provided blood samples two to three weeks after the first and second dose of vaccination and two months after the second dose..
In the lab, the researchers tested neutralizing antibodies by measuring whether a blood sample could block the interaction between the virus’s spike protein and the angiotensin-converting enzyme 2 receptor. This interaction is how the virus causes infection once it enters the body..
McDade, professor of anthropology, said: “When we tested blood samples from participants about three weeks after the second vaccine dose, the average inhibition level was 98%, indicating a very high level of neutralizing antibodies.
Scientists tested emerging variables B.1.1351 (South Africa) and B.1.1.7 (UK) and P.1 (Brazil) and found that the level of inhibition of viral variants was much lower, ranging from 67 to 92% in the test samples collected two months after the second dose, and they also found that antibody responses decreased by about 20%, and that the antibody response to vaccination varies Based on previous injury history.
Individuals with clinically confirmed cases of MERS-CoV and multiple symptoms had a higher response level than those who tested positive but had mild or no symptoms..
“Many people and clinicians assume that any previous exposure to coronavirus will give the body immunity to re-infection and based on this logic, some people who have been previously exposed do not think they need to be vaccinated,” the researchers said. To only one dose of one of the Pfizer / Moderna vaccines“.
The researchers noted: “Our study shows that prior exposure to the Corona virus does not guarantee a high level of antibodies, nor does it guarantee a strong antibody response to only the first vaccine dose.“.