China reacted on Wednesday to the World Health Organization’s head’s “irresponsible” remarks that the country’s unyielding and more harsh “zero COVID” policy is “not sustainable.”

The strategy has restricted movement for hundreds of millions of people in dozens of cities, most notably in Shanghai, inflicting enormous economic loss in China and elsewhere and fueling widespread dissatisfaction.

Shanghai officials stated on Wednesday that half of the city had reached “zero COVID” status, but restrictions will continue in place. The city is currently in its sixth week under a broad lockdown.