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What Is COVID-19 Super Immunity?
The concept of Covid-19 was introduced by researchers towards mid-2021 who observed a unique vaccination response in people that had already contracted the virus since the emergence of the pandemic. Immunologists reported an immense rise in antibodies that was significantly more than expected through double doses of Covid-19 vaccinations. Researchers termed it Covid-19 Super Immunity or Hybrid Immunity and delved deeper into its mechanism and role in future strains of viruses and the design of emerging antibodies.
Mechanism of Covid-19 Super Immunity
It is important to have an idea of the Covid-19 virus to understand the mechanism of super Immunity. In addition to the virus entering the body through the ACE-2 receptors of the body, the Sars-CoV2 non-structural proteins bind to the 40S ribosomal subunit of the host cells and cause the shutdown of mRNA translation in host cells and block the key mediators of host innate immune response of the body.
Covid vaccines work by stimulating a response from the immune system to the Sars Covid virus and creating a memory in the immune system, which helps the body remember the virus and protect itself from its implications. A number of studies, both human and animal, related to Sars-Covid vaccines have shown that they elicit a neutralizing antibodies (involved in the defence mechanism of the body) response to carry out their functions in addition to mediating T-cell responses for improved efficiency.
Neutralizing antibody responses from 104 vaccinated individuals in clinical trials including those with breakthrough infections, hybrid Immunity or without any history of vaccinations covid infection have shown that the human immune Sera (serum rich in antibodies) plays an important role in neutralizing the Sars-Covid variants. The additional antigen exposure from the natural infection coupled with the vaccination response boosts the quality and quantity of antibody-mediated immune response to manage covid-related systemic complications and build a strong defence mechanism.
What do Studies say about Covid-19 Immunity?
In trials conducted to observe the effects of super Immunity related to the covid virus, fully vaccinated healthcare workers previously diagnosed with Sars-Cov-2 were sequentially recruited at the Oregon Health and Science University for a period of 7 months between January 31, 2021 - August 18, 2021. Researchers took care to include subjects with a negative result for nucleocapsid antibodies because of their increased sensitivity to spike protein antibodies and possible association with a false positive report.
Fully vaccinated individuals who had not yet contracted the viral infection and who matched the recruited subjects in genders, age, time between vaccine doses, time between sample collection and most recent antigen exposure were included as controls. A full-length viral genome sequencing method was used to determine the SARS-Covid-2 variant identity. ELISA method was used to determine the concentration of IgG, IgA and IgM antibodies, identifying individuals with an adaptive immune response to SARS-CoV-2, and indicating recent or prior infection with Covid-19.
In addition to the original Sars-Covid-2 strain, other variants of concern, like the Alpha, Beta, Gamma and Delta strains, were used to determine the neutralizing serum dilution titers and properly evaluate the vaccination effectiveness. The study was conducted with the approval of Oregon university after taking written informed consent from the subjects.
Among the Twenty-six subjects with a mean age of 38 years, out of which 20 were females. Twenty-four subjects were vaccinated with BNT162b2, popularly referred to as Pfizer–BioNTech COVID-19 vaccine. These subjects were sampled for antibodies in the initial period of 28 days after collecting the PCR swabs from the nasal and nasopharyngeal regions and then resampled 213.5 days after the final vaccination.
All of the subjects that were sampled twenty-eight days after the final vaccination were compared with the controls to draw accurate results from the trial-based study. The results showed an immense increase in the total receptor-binding domain-specific immunoglobulin of almost in comparison to controls with a significant increase in the levels of IgG and IgA antibodies. For example, the median IgA EC50 after breakthrough infection was 120 compared with 24 for controls. IgM levels were not significantly different between either subject or control groups included in the study.
The increase in the antigen levels was observed for Delta and non-delta infections in the Focus Reduction Neutralization Tests though less than the antigens produced in the original Sars Covid variant; for e.g. FRNT scores were 4646 for the SARS Covid Variant in comparison to a score of 2482 in the Delta Variant. The Sera (Serum containing Antibodies) obtained from the Delta diagnosed cases showed improved potency of 99% against the Delta variant of Sars Covid-19 in comparison to a 36%potency observed for non-Delta cases with a 41% potency in the control group.
The study showed that there was a significant boost in humoral Immunity (caused by antibodies) after the infection, irrespective of the severity of the disease. Among the three antibodies measured, IgA antibodies were increased significantly, as was attributed to the differences in the route of exposure between natural infection and through vaccination. Sera concentrations obtained from the subjects and controls further showed improved variant cross-neutralization antibodies. This was a significant finding as cross-neutralizing antibodies bind specific sites on the spike protein and limit the virus from escaping any single antibody target.
The antibody increase in the Delta variants was considered especially significant as researchers learnt that the protective immune response or Covid- super Immunity can be further improved by developing boosters with antigenic inserts that match the emerging SARS-Covid variants adequately.
The fluke in the study was the fact that it was conducted for a short-term period of 6 months. Long-term monitoring of the immunological status of patients with Covid-19 with varying severity of symptoms and of people with low Sars-Covid-19 virus load is often not conducted because of patient irregularity and other factors. With the aim to establish the presence of IgA antibodies in the body of Covid positive patients, a nine-month monitoring of SARS-CoV-2 infection immune response development and extinction using quantitative assessment of IgA and IgG levels in the blood of healthy donors living in the context of the coronavirus pandemic and of the patients who have undergone COVID-19 was conducted.
One hundred eighty volunteers were included, out of which 51 contracted the Covid virus during the observation period. 20 of the 51 affected individuals showed an increase in the plasma anti-SARS Covid IgA levels that persisted for more than 6 months. In 17 of the 51 subjects, the IgA levels exceeded the levels of IgG antibodies. The study showed that irrespective of the vaccination status, IgA antibodies appeared earlier and showed a stronger and more robust response to the SARS-CoV-2 virus than IgG, with increased levels of IgA persisting throughout the nine months of the study.
Does it work for the Omicron Variant?
Omicron is one of the recent variations of Sars Covid that has been designated by the WHO as the variant of concern because of its easy transmissibility coupled with the severity of symptoms. What has increased the concerns of healthcare experts is the marked vaccine reduction added to the increased risk of reinfection observed in this particular Covid-19 variant.
Fortunately, Covid super Immunity can work even in Omicron conditions by strategically planning the vaccination periods after the infection. In order to assess the Omicron variant neutralization susceptibility, researchers collected blood samples from subjects who had taken the vaccines or from those who had suffered from breakthrough infections by Alpha/Delta virus strains who were vaccinated prior to the infection.
Conclusion
The results showed that Omicron was highly resistant to neutralization in fully vaccinated individuals who had not contracted the infection. That said, a cross-neutralization pattern against Omicron was induced in vaccines in people who had contracted the virus. Throughout the study, the time interval between the vaccination and infection played an important role in building Covid Super immunity in the person and increased the strength of the antibodies to a significant extent.
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