One of China’s top government health officials has repeatedly promoted Covid-19 remedies included in Beijing’s official treatment protocol for the disease without disclosing his links with the manufacturers.

Epidemiologist Zhong Nanshan was appointed to head an expert group at the National Health Commission, the body responsible for formulating China’s health policy, at the start of the pandemic and is considered a hero in the country after managing the Sars epidemic in 2003.

The NHC publishes an official protocol that advises on Covid treatments and medicines that is regarded as the treatment “bible” by doctors and local governments across China, according to Jin Dong-Yan, a virologist at the University of Hong Kong.

But Zhong has close ties to the companies behind some of the treatments, which he has promoted in scientific journals and in public talks without mentioning these relationships.

“It’s one thing to propose something to be included in the treatment guidelines based on evidence, but it’s another thing if you have a commercial interest in proposing the inclusion, because the latter suggests a conflict of interest you should avoid,” said Yanzhong Huang, a senior fellow for global health at the Council on Foreign Relations think-tank.

Philip Chan, a committee member of Pharmacists Connect, a Hong Kong organisation that represents the sector, added: “If [Zhong] is promoting products, he should explain clearly the interests that he has with . . . the company behind the product.”

There is no suggestion that Zhong has behaved illegally and he is not the only public health official in China who works with the private sector. But his high profile and influence over the country’s response to the pandemic mean the general population follows his advice, according to Huang.

Zhong and the NHC did not respond to requests for comment.

Xuebijing, a traditional Chinese medicine made by Shenzhen-listed Tianjin Chase Sun Pharmaceutical, was added to the NHC’s protocol for treating Covid in January 2020. The company’s share price has subsequently risen about 48 per cent, boosting its stock market capitalisation by Rmb6bn ($919mn).

According to an article from the newspaper of the Chinese Medical Doctor Association, the leading professional body, Xuebijing was included in the NHC’s treatment protocol after Zhong proposed to research its effectiveness.

Zhong has continued to promote the treatment.

“Preliminary results show [Xuebijing is] effective . . . It not only relieves symptoms but also reduces death rates,” Zhong said at a health event held by Tencent, the technology group, in April 2020.

Zhong co-authored a study about the benefits of using Xuebijing in Chinese Critical Care Medicine, a peer-reviewed scientific journal, last year. “Conventional therapy combined with Xuebijing injection can significantly improve the . . . clinical prognosis of patients with severe” Covid-19, the study said.

But Zhong did not declare that he is a director of Tianjin Hongri Jiandakang Pharmaceutical Technology, a company in which Xuebijing manufacturer Tianjin Chase Sun Pharmaceutical has a 12.5 per cent stake, according to Tianjin Chase Sun’s financial reports and corporate records.

Zhong Nanshan Medical Foundation of Guangdong Province, a charity founded in 2011 that conducts medical research and public health activities, also holds a 6.25 per cent stake in Tianjin Hongri Jiandakang. Yao Xiaoqing, Tianjin Chase Sun’s chair and legal representative, is a director of Tianjin Hongri Jiandakang.

Tianjin Chase Sun Pharmaceutical, Tianjin Hongri Jiandakang Pharmaceutical Technology and Chinese Critical Care Medicine did not respond to a request for comment.

Zhong has also extolled the benefits of another traditional Chinese medicine, Lianhua Qingwen, which was added to the official protocol on January 27 as a Covid treatment.

The treatment is made by Shijiazhuang Yiling Pharmaceutical, a Shenzhen-listed company whose stock has since risen about 146 per cent, buoying its market capitalisation by more than Rmb26bn.

Lianhua Qingwen “is effective in treating mild and moderate [Covid] symptoms. Not only domestically, we can also promote it overseas,” Zhong said at the Tencent event.

Two boxes of the product were distributed to all Hong Kong residents during a recent Omicron outbreak that swept through the city.

Zhong has a longstanding relationship with Shijiazhuang Yiling and Wu Yiling, its billionaire founder. The company donated Rmb130,000 to the Zhong Nanshan Medical Foundation in 2013 and Zhong and Shijiazhuang Yiling signed a “strategic co-operation” agreement to research the benefits of Lianhua Qingwen two years later.

In 2019, Zhong and Wu opened a separate joint research centre, an initiative of Shijiazhuang Yiling and Guangzhou Medical University, where Zhong previously served as president.

Zhong co-authored a paper in May 2021 on the effectiveness of Lianhua Qingwen with Jia Zhenhua, Wu’s son-in-law, for Phytomedicine, a scientific journal owned by Dutch academic publisher Elsevier, without disclosing that the two were connected to the company. “Our findings indicated that Lianhua Qingwen capsules could be recommended to patients with Covid-19 for reducing the symptom burden and improving clinical outcomes,” the paper’s authors wrote.

The journal added a correction following complaints from academics to make clear Zhong’s ties to Jia but did not mention his links to Shijiazhuang Yiling.

“After being made aware of concerns regarding insufficient declaration of potential competing interests regarding this paper, the journal investigated,” Elsevier said. “As a result of the investigation, the editor in chief approved the published corrigendum.”

Phytomedicine declined to comment on why it did not clarify Zhong’s links to Shijiazhuang Yiling.

Shijiazhuang Yiling confirmed it had made donations to the foundation but said it was a charity and Zhong’s personal interests were “irrelevant”. The company added that Zhong did not receive any funding for the strategic co-operation agreement to study Lianhua Qingwen.

“It’s a problem because these people now have a personal financial stake in the findings of the study,” said Trish Greenhalgh, a health sciences professor at the University of Oxford who has published research showing that studies on Lianhua Qingwen and Xuebijing have not proved they are effective Covid treatments.

The US Food and Drug Administration has said claims that Lianhua Qingwen could prevent or treat Covid were “not supported by competent and reliable scientific evidence”.

Zhong has also recommended the use of a nebuliser made by Asclepius Meditec, a Chinese device maker, that helps patients to inhale a mix of hydrogen and oxygen to treat coronavirus. The treatment was added to the official protocol in March 2020.

Zhong is an official adviser to the company and his endorsement is used in its advertising for the product.

He co-authored a paper in June 2020 in the Journal of Thoracic Disease, where he is editor-in-chief, that found there were clinical benefits in using Asclepius Meditec’s device but did not disclose his links to the company.

Zhong co-authored a separate paper in the journal Engineering in October 2020 which stated that studies he co-wrote on Lianhua Qingwen and the nebuliser were reasons for their inclusion in China’s official treatment protocol. Zhong did not declare that he is an official adviser to the company.

Asclepius Meditec, the Journal of Thoracic Disease and Engineering declined to comment.