4.5  Vaccine development
After SARS, development of a vaccine appeared to be the best approach to prevent future SARS-CoV epidemics. However, there were many obstacles in SARS vaccine development. Firstly, researchers did not have a comprehensive understanding of the pathogenic mechanism of SARS-CoV. Secondly, animal models of SARS-CoV infection could not simulate human disease because of an incongruent pathogenesis. Thirdly, in order to test the efficacy, many people must be tested in areas where the virus is endemic. Once the SARS epidemic ended, human trials were not possible [59]. Although several candidate vaccines against SARS-CoV have been produced and tested, at present, unfortunately, there is no FDA approved vaccine against SARS.