BEIJING – More than two dozen Chinese parents protested Monday in front of a government building in Beijing to protest a vaccine scandal that has become one of the most visible public health crises in China in recent years
Month that hundreds of thousands of children in China had been injected with flawed diphtheria, tetanus and whooping cough vaccines.
While the children remained unhurt, the episode undermined President Xi Jinping's vision of a newly resistant China and its promise to eradicate corruption and abuse in the country's food and drug industry.
"The problem is not solved," said He Fangmei, the mother of a two-year-old girl's telephone interview after the protest. "Our concerns were not addressed."
The recent crisis is the third one affecting vaccines in China since 2010. To restore confidence in China's vast pharmaceutical industry, Mr. Xi has ordered a nationwide investigation of vaccine manufacturers.  Police on Sunday announced plans to arrest 18 employees of the vaccine manufacturer in the center of the Changchun Changshang scandal in northeastern China, including company chairman Gao Junfang.
Authorities say the company violated standards in the production of more than 250,000 doses of diphtheria, whooping cough and tetanus vaccines and manipulated with data in the production of a rabies vaccine. The vaccines were not harmful to health, according to the authorities, but the children were at risk of contracting diseases they should have been protected against.
Another company involved in the scandal is accusing the Wuhan State Institute for Bioproducts in central China of producing more than 400,000 vaccines that did not meet the standards.
While regulators forced the Wuhan Institute of Biological Products to pay a fine, many parents expressed their concern that the authorities had not punished the company more severely because of its government relations.
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 over the past few decades has helped eliminate polio and drastically reduce the spread of other diseases.
The protests on Monday, coupled with a burst of anger in social media in recent days, suggested that many parents had doubts about allowing their children to be injected with Chinese-made vaccines
Dr. Gauden Galea, the representative of the World Health Organization in China, said that the fact that the defective vaccines were discovered by the investigators for the Chinese Food and Drug Administration shows that the country's regulatory system is working. But he said that the government, which often prefers secrecy in investigations, must be transparent in order to restore confidence in vaccinations.
"You have to ask and answer more questions than the population asks to regain the trust." he said
The protests on Monday posed an unusual challenge for the government, which has used censors to restrict the discussion of the vaccine crisis online
. Xi, China's most powerful leader for decades, has sought to justify its top-down rule with the promise of a higher standard of living. But analysts say incidents like vaccination uprisings could damage its credibility.
Merriden Varrall, an expert on China at the Lowy Institute, a research organization in Australia, said that many Chinese families have only one child, scandals that involve potential. Child harm is considered particularly outrageous.
"How is that in a China that is told to people, really on the path of rejuvenation?" She said. "Scandals like these are just not accepted anymore."
Follow Javier C. Hernández on Twitter: @HernandezJavier .
Iris Zhao and Elsie Chen did research work.