Shares in one of China's largest traditional medicine producers plunged on Monday after reports questioned the efficacy of pills approved by the government as a coronavirus treatment.
Shanghai authorities have joined their Hong Kong counterparts in handing out 'Lianhua Qingwen' -- a herbal remedy marketed for fever and sore throats -- as the cities battle their worst Covid-19 outbreaks since the pandemic's start.
But on Sunday, popular Chinese health platform Dingxiang Yisheng said the capsules, made by Shijiazhuang Yiling Pharmaceutical, could not prevent cases of the virus, in a report then picked up by state media.
Monday's share dump sent them falling to 32.39 yuan ($5) with the stocks hitting the daily limit of 10 per cent on the Shenzhen exchange.
Last week, Wang Sicong, an influencer and son of one of China's wealthiest scions, ignited debate about the drug on Weibo when he reposted a social media video questioning whether the World Health Organization had ever recommended it for use against Covid-19.
The United States and other countries have warned there is no evidence the medicine works to prevent or cure coronavirus, even as it has increasingly been promoted by government authorities in China and Hong Kong.
The US Food and Drug Administration has said it has not approved Lianhua Qingwen, and that coronavirus-related claims about it were "not supported by competent and reliable scientific evidence".
In 2020, Beijing approved the remedy -- initially developed for SARS and made up of ingredients like honeysuckle and apricot seeds -- as a coronavirus treatment.
In financial centres Hong Kong and Shanghai, which are struggling to quash fast-spreading Omicron-fuelled surges, boxes of Lianhua Qingwen tablets have been included in government care packages.
Hong Kong Chief Executive Carrie Lam even claimed last month that traditional Chinese medicine may be more effective than Western medicine at preventing Covid and accelerating recovery.
Shanghai, China's largest city, has been locked down since March as cases have topped 25,000 a day -- low compared with parts of the world now living with the virus, but virtually unheard of under China's "zero-Covid" strategy.
At the peak of its Omicron-driven outbreak last month, Hong Kong was recording one of the world's highest mortality rates from the virus.
