"Nothing has set back China’s preparations as extensively as its difficulty in vaccinating older people. Two-thirds of people ages 80 and older are vaccinated, but only 40 percent have received a booster dose, a critical shortcoming because Chinese-made vaccines offer weaker protection than the Pfizer-BioNTech and Moderna vaccines."

https://www.nytimes.com/2022/12/02/health/china-covid-lockdowns.html