Stricter inspections of Chinese vaccine manufacturers have caused a shortage of flu vaccines, raised the risks of widespread infections and highlighted the lack of staff at the country’s top pharmaceutical regulator.

China’s drug administration has required vaccine manufacturers to undergo on-site inspections after it was discovered in July that two Chinese companies had sold hundreds of thousands of substandard rabies and diphtheria, pertussis and tetanus (DPT) vaccines.

Changsheng Biotech, the company at the centre of the scandal, accounted for about 15 per cent of China’s flu vaccine production last year and has been ordered to halt production. A lack of staff able to carry out online inspections at other producers has delayed approvals, according to analysts and industry insiders.