The Emergence of Hybrid Variants of SARS-CoV-2: Towards Hybrid Immunity

In this review work, the authors emphasize the discussion on different emerging variants of SARS-CoV-2 and vaccine effectiveness against them [...].

Vaccines 2023, 11, 764 2 of 4 electroluminescence immunoassays can be modified and improvised for rapid detection of new emerging hybrid variants [10]. numerous immunological and serological assays like ELISA, Chemiluminescent assays, neutralization assays, flow cytometry and electroluminescence immunoassays can be modified and improvised for rapid detection of new emerging hybrid variants [10].
Studies have reported a lower rate of replication of the virus in vaccinated individuals compared with the non-vaccinated population. The continued emergence of novel hybrids of SARS-CoV-2 is contributed to by the large number of unvaccinated populations comprising children, adults, immunocompromised individuals and aged people. The virus circulates in the non-vaccinated population which provides it conducive environment to survive, evolve and propagate [11]. Due to the worldwide expansion of SARS-CoV-2, the inability of virus-and vaccineinduced immunity to inhibit transmission, together with the formation of antigenically different variations, has prevented the achievement of herd immunity against SARS-CoV-2. According to Evans JP and co-workers [5], "Compared to the reaction to the D614G variation, neutralizing-antibody titers with mRNA vaccine against the BA.3 variant and the deltacron variant were 3,3 and 44,7 times lower, respectively." The vaccine from Pfizer proves to be ineffective against XE variants [12]. Bates et al. demonstrated that SARS-CoV-2 infection before or after immunization offers a considerably higher increase in the neutralizing antibody response compared with two doses of vaccine alone against the different emerging viral variants [13]. To obtain the same level of humoral immunity as hybrid Studies have reported a lower rate of replication of the virus in vaccinated individuals compared with the non-vaccinated population. The continued emergence of novel hybrids of SARS-CoV-2 is contributed to by the large number of unvaccinated populations comprising children, adults, immunocompromised individuals and aged people. The virus circulates in the non-vaccinated population which provides it conducive environment to survive, evolve and propagate [11].
Due to the worldwide expansion of SARS-CoV-2, the inability of virus-and vaccineinduced immunity to inhibit transmission, together with the formation of antigenically different variations, has prevented the achievement of herd immunity against SARS-CoV-2. According to Evans JP and co-workers [5], "Compared to the reaction to the D614G variation, neutralizing-antibody titers with mRNA vaccine against the BA.3 variant and the deltacron variant were 3.3 and 44.7 times lower, respectively." The vaccine from Pfizer proves to be ineffective against XE variants [12]. Bates et al. demonstrated that SARS-CoV-2 infection before or after immunization offers a considerably higher increase in the neutralizing antibody response compared with two doses of vaccine alone against the different emerging viral variants [13]. To obtain the same level of humoral immunity as hybrid immunity, a third dose of vaccination is required, and hence provides a protective precedence [14]. A retrospective cohort study concluded that vaccine-induced hybrid immunity provides better protection against emerging variant-induced hospitalization than natural immunity [15]. The omicron form exhibited a significant decrease in the neutralizing capacity of both vaccination-induced and vaccine-plus-infection-induced antibodies which could indicate immunological evasion [16]. Booster dosing with mRNA vaccine demonstrated 25% more immune protection against such hybrid variants than with fully vaccinated individuals [17]. Such genetic recombination will be broadly influenced by high transmissibility and immune evasion. This action will begin in the upper respiratory tract with visible symptoms. The symptomatic and asymptomatic host can be treated with sterile immunity, comprising secretory IgA and cellular immunity, through widespread intranasal vaccination [18]. Although reports reveal that all forms of immunity diminish over time and are inefficient in protection from re-infection. However, they do lower the rates of hospitalization and the severity of the infection. The population with hybrid immunity is found to demonstrate greater protection [19].
The pandemic risk posed by the emerging new variants is the greatest obstacle in the construction of immunizations and antiviral medications with enhanced effectiveness and larger penetration. Therefore, it is crucial to develop effective strategies for tackling the concern of the new pandemic caused by emerging novel variants. Consequently, these developments will lead to advancements in the healthcare domain improving the pharmacological aspects. The improved vaccination scenario and repeated exposure to new variants will become important promoters of hybrid immunity in the global population.
Author Contributions: V.P.C. created the plot of the manuscript and wrote the first draft with all the authors. Figure 1 is created with Biorender.com. All authors have read and agreed to the published version of the manuscript.
Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.