There are fears for the safety of a woman campaigning about China’s defective vaccines, with activists saying she has been missing for more than 40 days. Authorities have been clamping down on families demanding redress over hundreds of thousands of doses issued by the government.

Following revelations in July that a state-sponsored vaccine programme had been using faulty serum, Tan Hua, 38 had been organising parents calling for compensation and changes to how health authorities manage vaccines.

It is one of the largest public health scandals to hit China since the discovery of melamine-tainted baby formula in 2008. Changsheng Biotechnology, based in China’s northern province of Jilin, was found to have sold 250,000 defective vaccines. It also fabricated inspections dating back to 2014. Another major vaccine maker, the state-owned Wuhan Institute of Biological Products, was also producing faulty inoculations for infants.

Tan, who claims she is the victim of a defective rabies vaccine in 2014 and has been protesting for years, was among a group of at least nine other protesters who were detained after attempting to protest in Beijing’s Tiananmen Square in early September at the time of a China-Africa summit in the capital.

He Fangmei, another campaigner, who was with Tan at the time, said: “Some 10 or 20 men in plain clothes surrounded us and caught Tan Hua. I was trying to make calls to other activists for help.” He, who says her daughter became partially paralysed after receiving one of the substandard vaccines discovered this year, was sent back to her home province of Henan.

Unlike the others who were released or whose family members have received notice of their detention, there has been no news of Tan since she was taken away on 3 September. She reportedly has epilepsy and other health problems and had been seeking compensation in Beijing for disability. “Tan Hua is the only who totally disappeared without any information,” said He.

Authorities have tried to respond swiftly to the latest vaccine scandal, firing senior officials in China’s Food and Drug Administration and detaining the chairwoman of Changsheng as well as more than a dozen other employees. President Xi Jinping promised the government would “investigate to the end” and “effectively respond to the concerns of the people”.

Some have been beaten. Some have been detained. Some are terrified. He Fangmei, vaccine campaigner

Yet parents who have become vocal, calling for a vaccine law or more information about vaccine safety, have come under pressure to keep quiet.

“Authorities simply refuse to work with citizens, even on issues where they are allied,” said Frances Eve, a campaigner with the advocacy group Chinese Human Rights Defenders. “That the [Chinese Communist] party would rather lock up a victim of a very scandal its trying to fix shows it still doesn’t know how to protect social-economic rights.”

Qi Jing, a single father in Chongqing, in south-western China who has also been campaigning, says police have visited his home three times in the last month. Wechat group of about 300 parents, advocates and vaccine victims, used to mobilise protest, has been censored, according to He. He, Tan and others who had been protesting outside the gate of the National Health Commission, State Drug Administration in Beijing since the end of July have halted their activities since the detentions.

“Our group of activists is like a plate of scattered sand. Some have been beaten. Some have been detained. Some are terrified. I will of course keep fighting for my daughter, but to be honest, I have no idea what to do,” she said.

