The Chinese Center for Disease Control and Prevention is thinking about mixing vaccines and varying the sequence of doses to boost efficacy. It is the first time a government body has discussed publicly that there are concerns over the effectiveness of Chinese jabs.

Gao Fu, CDC head, told a forum on Saturday that the agency was “considering how to solve the problem that the efficacy of existing vaccines is not high”, according to local media.

In a now unavailable Weibo social-media post, the influential Vaccines and Science account said Gao’s comments were “very candid”. But it also reminded readers that taking the jab was still important for protecting the country. It added that “we can’t wait for vaccines to become perfect before getting vaccinated”.