BEIJING — More than two dozen Chinese parents, shouting phrases including “Justice for the victims,” gathered outside a government building in Beijing on Monday to protest a vaccine scandal that has become one of the most visible public health crises in China in recent years.
The protest followed reports this month that hundreds of thousands of children across China had been injected with faulty vaccines for diphtheria, tetanus and whooping cough.
While the children appear to be unharmed, the episode undermined President Xi Jinping’s vision of a newly resilient China and his vow to eliminate corruption and abuse in the nation’s food and drug industries.
The protesters, standing outside the offices of the National Health Commission, called for stricter oversight of China’s drug industry, according to interviews with parents and images posted on social media. Holding a banner showing photos of children, the demonstrators rejected assurances by Chinese leaders that the issue was under control.
“The problem is not solved,” He Fangmei, the mother of a 2-year-old girl, said in a telephone interview after the protest. “Our concerns have not been addressed.”
The latest crisis is the third involving vaccines in China since 2010. In a bid to restore confidence in China’s vast pharmaceutical industry, Mr. Xi has ordered a nationwide investigation of vaccine producers.
The police on Sunday announced plans to arrest 18 employees of the vaccine producer at the center of the scandal, Changchun Changsheng, in northeastern China, including the company’s chairwoman, Gao Junfang.
The authorities say the company violated standards in producing more than 250,000 doses of the vaccines for diphtheria, whooping cough and tetanus, and tampered with data in producing a rabies vaccine. While the vaccines were not harmful, officials say, they left children at risk of contracting illnesses that they should have been protected against.
Another company involved in the scandal, the state-owned Wuhan Institute of Biological Products in central China, is accused of producing more than 400,000 vaccines that did not meet standards.
While regulators forced the Wuhan Institute of Biological Products to pay a fine, many parents express concern that the authorities have not punished the company more severely because of its government ties.
Public health experts say the problems at the two companies could lead to a broader backlash against vaccines in China, where an aggressive immunization effort in recent decades has helped eliminate polio and drastically reduce the spread of other diseases.
The protests on Monday, coupled with an outpouring of anger on social media in recent days, suggested that many parents were having doubts about allowing their children to be injected with vaccines made in China.
Dr. Gauden Galea, the representative of the World Health Organization in China, said the fact that the faulty vaccines had been discovered by investigators for the China Food and Drug Administration showed that the country’s regulatory system was working. But he said the government, which often favors secrecy in investigations, would need to be transparent to restore faith in immunizations.
“They need to ask and answer more questions than the population is asking in order to earn the trust back,” he said.
The protests on Monday were an unusual challenge to the government, which has deployed censors to limit discussion of the vaccine crisis online.
Mr. Xi, China’s most powerful leader in decades, has sought to justify his top-down rule with promises of higher living standards. But analysts say that incidents like the vaccine uproar could damage his credibility.
Merriden Varrall, an expert on China at the Lowy Institute, a research organization in Australia, said that because many Chinese families have only one child, scandals that involve potential harm to children are considered particularly egregious.
“How is this still happening in a China that people are told is really on track for rejuvenation?” she said. “Scandals like this are simply not going to be accepted as par for the course anymore.”
Follow Javier C. Hernández on Twitter: @HernandezJavier.
Iris Zhao and Elsie Chen contributed research.