@jerry aiyo that's why they need a stronger booster like Cansino...it's already been done in China and only recently made official announcement. Read the articles (esp. the Chinese links) I posted earlier, Sinovac+Cansino efficacy is 6x higher than homologous booster. Mix and match booster induces stronger antibody protection against Delta and Omicron compared to a 3rd dose of Sinovac vaccine.

https://www.theedgemarkets.com/article/china-start-using-mixandmatch-covid19-vaccine-booster-method