Coronavirus disease 2019 vaccines: challenges of using global mass vaccination to achieve herd immunity

According to World Health Organization (WHO), the vaccines procured the most are Comirnaty (Pfizer BioNTech, America-Germany), Spikevax (Moderna, America), Vaxzevria (AstraZeneca, Britain), Covishield (SII, India), and CoronaVac (Sinovac, China). The subsequent activation of innate immunity can theoretically generate pro-inflammatory cascades, for instance, inflammasome formation and activation of the nuclear transcription factor-kappa B pathway. With up to 37 amino acid mutations on its S protein, the spike protein of the Omicron mutant exhibits a stronger binding ability to angiotensin-converting enzyme 2, which explains the potential mechanism underpinning its enhanced infectivity. [...]Omicron is believed to be associated with a higher risk of reinfection and a significantly enhanced immune escape ability, although the underlying mechanism remains unclear. Previous infections cannot protect individuals from the epidemic due to the constant mutations of the virus. [...]many countries that used to develop herd immunity by the natural infection have now resorted to the weapon of vaccines.