A COVID-19 outbreak in the Chinese city of Nanjing is worse than Wuhan’s initial cases, state media says, leading officials to wonder if China’s vaccines are effective. According to officials, the outbreak of the Delta variant has led to longer lines for testing, with residents asked to wear masks, social distance, and leave the chit-chat at home. Almost 200 people have been infected since July 20, with seven of those in critical condition. The sudden outbreak has increased fears that China’s homegrown vaccines, which were believed to be 50 percent to 79 percent effective in preventing symptomatic COVID-19, have been stunted by the Delta variant. Other Asian countries using the vaccines have sought doses from other providers as a result.

Officials have traced the outbreak to the Nanjing airport, where they believe a crew cleaning an inbound flight from Russia to be responsible as they didn’t adhere to hygiene protocols. The airport has been closed, with all flights suspended through Aug. 11, according to the BBC.