**3. Concluding remark**

The emergence of SARS-CoV-2 signals an emergency for the global health care system. Emerging recent COVID-19 waves and causalities worldwide are due to breakthrough infection among vaccinated or unvaccinated individuals, which demonstrated a reduction in vaccine response in neutralising virus infection, but the hospitalisation rate is significantly lower among those who completed vaccination dosages. The high transmission rate and vaccine breakthrough capability of VOCs, particularly the delta and omicron variants, are the reasons for the community's global spread. During the detla and delta plus waves in India, the situation was

critical, and many people were hospitalised and died. Recently emerged Omicron or its sub-lineages have shown multiple re-infections and breakthrough infections due to their high transmissibility and immunological escape from neutralising antibodies produced by prior infections or vaccinations. Vaccines respond differently to each variant of concern. The effectiveness of booster vaccinations is decreasing over time, although it has been enhanced with successive booster doses. The vaccinations are very successful in reducing recipients' risk of developing severe illness due to COVID-19. Overall, despite vaccination efforts, many countries experienced the consequences of omicron variants, and since SARS-CoV-2 tends to mutate and adapt in our community, the emergence of highly transmissible and deadly strains of COVID-19 variants cannot be ruled out. Understanding the origin, transmission, and breakthrough infections of the SARS-CoV-2 variant may allow us to better prepare for future pandemics.
