We can expect additional waves depending on multiple factors. Epidemics and pandemics subside when a percentage of population have immunity against the organism acquired either through natural infection or vaccination. This is called as herd immunity. It depends on the infectivity (R0) of the virus and is given by the equation 1-1/R0. Assuming that Delta virus has R0 value of 8, herd immunity will be achieved when 87.5% of the population has evidence of immunity. Original strain had an R0 value of ~2.3; hence, herd immunity level is achieved at 56.5%. Second factor is the duration of effective immunity following natural infection and vaccination. Immunity may wane over time. Third factor is the emergence of new variants that evade the existing immunity. Fourth factor is the weak immune system in certain people. Fifth factor is whether people are following Covid appropriate behaviour or not.
Can we expect any more COVID-19 waves after the second wave?
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