A new study found that two months following the second Pfizer/Moderna vaccination, the antibody response in persons with prior episodes of COVID-19 falls by 20%. Additionally, the study assessed the resistance of current vaccinations to new variations.
The study’s findings were published in the scientific journal ‘Scientific Reports’.
The Northwestern University study emphasised the necessity of taking a second dose of vaccine, not just because protection to immunizations diminishes with time, but also because of the risk posed by new variants, such as the highly contagious delta variant.
Additionally, the study demonstrated that past exposure to SARS-CoV-2 does not ensure high antibody levels or a robust antibody response to the initial vaccine dose.
This directly contradicts the belief that contracting COVID automatically renders an individual immune to re-infection. The findings reinforce the need of immunisation (and two doses), even for persons who have previously had the virus.
A team of scientists, led by biological anthropologist Thomas McDade and pharmacologist Alexis Demonbreun, tested blood samples from adults who tested positive for SARS-CoV-2 to determine the duration of immunity conferred by the Pfizer and Moderna vaccines and their ability to protect against newer variants.
Participants were recruited at the outset of the epidemic from a racially and culturally diverse community-based sample of Chicago-area adults.
Participants gave blood samples two to three weeks after receiving their first and second doses of vaccination, as well as two months after receiving their second dose, using at-home antibody testing kits produced in the lab.
The researchers determined whether the blood sample possessed neutralising antibodies by examining its ability to disrupt the connection between the virus’ spike protein and the ACE2 receptor – this interaction is how the virus causes infection after it enters the body.
“When we tested blood samples from participants about three weeks after their second vaccine dose, the average level of inhibition was 98 percent, indicating a very high level of neutralising antibodies,” said McDade, an anthropology professor in the Weinberg College of Arts and Sciences and a faculty fellow at the University’s Institute for Policy Research.
The researchers investigated developing variants B.1.1351 (South Africa), B.1.1.7 (United Kingdom), and P.1 (Brazil) and discovered that the amount of inhibition against viral variations was much lower, ranging from 67% to 92%.
They discovered that antibody responses dropped by roughly 20% in samples obtained two months following the second dosage.
The researchers discovered that the antibody response to vaccination varied according to past infection history.
Individuals with clinically proven COVID-19 infection and various symptoms responded more strongly than those who tested positive but had minor symptoms or were asymptomatic.
“Many people, including many physicians, believe that earlier exposure to SARS-CoV-2 confers immunity against re-infection. According to this thinking, some individuals who have had prior exposure do not believe they need to be vaccinated “McDade explained.
“Or, if they do receive vaccination, they believe they only require the first dosage of the two-dose Pfizer/Moderna vaccinations,” McDade continued.
“Our study demonstrates that past exposure to SARS-CoV-2 does not ensure high antibody levels or a robust antibody response to the initial vaccine dose,” McDade concluded.
“The antibody response to vaccination is essentially the same for those who have had mild or asymptomatic infections as it is for persons who have never been exposed,” McDade explained.
McDade stated that while the research was conducted prior to the delta virus’s debut, the findings are comparable.
“In terms of protection following vaccination, the situation is the same for all varieties, including delta: the vaccine gives adequate protection, but not as much as the virus for which the vaccine was developed,” McDade said.
“When this is combined with the fact that immunity deteriorates over time, an increased vulnerability to breakthrough infection results. Thus, it is a case of two strikes at the moment — delta plus declining immunity among the first wave of vaccine recipients “McDade came to a conclusion.
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