Why scientists used monkeys to test the SARS vaccine?

Scientists used monkeys to test the SARS vaccine because non-human primates share a closer genetic and physiological similarity to humans, making them a more relevant model for studying the immune response and potential efficacy of the vaccine. Monkeys can also develop similar symptoms to humans when infected with the virus, allowing researchers to observe the vaccine's protective effects in a controlled environment. Additionally, ethical considerations and regulatory requirements often necessitate the use of animal models before advancing to human trials.