Commentary In the 1960s, measles was devastating in many parts of the world, with the child mortality rate as high as 50 percent. Scientists isolated the virus from patients and cultivated it in chicken embryo fibroblasts. This process, called the attenuation process, made the virus less virulent. Less virulent viruses are sometimes used as vaccines, known as attenuated vaccines. The attenuated measles vaccine was widely used after successful clinical trials in the 1960s. Later, it was combined with vaccines against mumps and rubella as the popular MMR  (measles, mumps, and rubella) vaccine. The development of attenuated vaccines is now less favoured against newly emerging diseases, as the risk (albeit small) is always there for the attenuated virus to regain virulence. New technologies such as the subunit vaccine, recombinant vaccine, and mRNA vaccine are now more often applied when developing new vaccines, as they do not contain live pathogenic virus. The Omicron …