A new study has been conducted to confirm the effects on the human body if the second dose of the Covid vaccine is not taken.
According to the research, two months after the second Pfizer/Moderna vaccination, the antibody response drops by 20 percent in adults with previous cases of COVID-19. The study also tested how well existing vaccines are resistant to emerging variants.
The results of the study were published in the journal Scientific Reports. A Northwestern University study emphasized the importance of receiving second dose from the vaccine, not only because it is generally known that immunity from vaccines diminishes over time, but also because of the risks posed by new and emerging variants, including the highly contagious delta variant.
The study also showed that prior exposure to SARS-CoV-2 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 having COVID will make a person naturally immune to re-infection.
The results also support vaccination (and two doses), even for people who have had the virus previously.
A team of scientists, including biological anthropologist Thomas McDaid and pharmacologist Alexis Demonbreun, tested blood samples from adults who tested positive for SARS-CoV-2 to measure how long the immune benefits of the Pfizer and Moderna vaccines last and how well they protect against the newer. variables.
Study participants were drawn from a racially and ethnically 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 the 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.
“When we tested blood samples from participants about three weeks after the second vaccine dose, the average level of inhibition was 98 percent, indicating a very high level of neutralizing antibodies,” said McDaid, professor of anthropology at Weinberg College of Art. and Science and Faculty Fellow at the University’s Institute for Policy Research.
The scientists tested the emerging variants B.1.1351 (South Africa), B.1.1.7 (UK) and P.1 (Brazil) and found that the level of inhibition of the viral variants was much lower, ranging from 67 percent to 92 percent. In test samples collected two months after the second dose, they found that antibody responses decreased by about 20 percent. The researchers found that the antibody response to vaccination varies based on a history of previous infection. Individuals with clinically confirmed cases of COVID-19 and multiple symptoms had a higher response level than those who tested positive but had mild or no symptoms.
“Many people and many clinicians assume that any previous exposure to SARS-CoV-2 will confer immunity to re-infection. Based on this reasoning, some people with previous exposure do not think they need to be vaccinated,” she said.
“Or if they are vaccinated, they think they only need the first of two doses of the Pfizer/Moderna vaccine,” McDaid added.
“Our study shows that prior exposure to SARS-CoV-2 does not guarantee a high level of antibodies, nor does it guarantee a robust antibody response to the first vaccine dose,” McDaid continued.
“For people who have had a mild or asymptomatic infection, their antibody response to the vaccination is basically the same as that of people who have not been exposed before,” McDaid explained.
McDaid added that although the research was conducted before the emergence of the Delta virus, the conclusions are similar. “In terms of post-vaccination protection, the story is the same for all variants, including delta — the vaccine provides good protection, but not as good protection as the original version of the virus the vaccine was designed for,” she said.
McDaid concluded, “Combining that with the fact that immunity diminishes over time, susceptibility to superinfection increases. So, there are two hits at the moment – delta plus weakened immunity between the first wave of vaccinations.”