China is giving Covid-19 booster vaccines using technologies different from the initial injections, in an effort to improve immunisation strategies amid concerns that its most-used jabs appeared to be weaker against variants such as Omicron.

Boosting population immunity could be crucial to preparing China to eventually reopen its borders and pivot from its “dynamic zero” strategy, which involves travel curbs and mass testing following dozens of local infections. Experts are watching whether combined Chinese doses would lead to higher effectiveness, Reuters reported.

Adults injected with a vaccine developed by Sinopharm or Sinovac at least six month earlier can now receive their booster doses with a vaccines using different technologies, produced by CanSino Biologics (CanSinoBIO) or a unit of Chongqing Zhifei Biological Products, National Health Commission official Wu Liangyou said.