Which of the following statements most accurately characterizes the virulence of the SARS-COV-2 virus between spring 2020 and summer 2022?
A. Vaccination enhanced host immune responses and reduced fatality rates,
B. which supports the hypothesis that SARS-Cov-2 has evolved reduced virulence .
C.Strains like the Omicron and Delta variants became prevalent because their lower virulence increased opportunities for direct transmission
D.Fatality rates fell, but probably not because the virus evolved lower virulence.