Chinese President Xi Jinping has called a scandal over inferior vaccines "vile" and "shocking." Many in China are scared and angry over lax regulations.
Chinese authorities have launched an investigation into a vaccination scandal that is sending shockwaves through the country.
Changsheng Biotechnology, the country's second-largest vaccine maker, was found to have produced sub-standard vaccines.
There is no indication anyone has been harmed by the vaccines, but the widening scandal has frightened people.
Read more: Sieren's China: Vaccines against trust
It has also brought renewed criticism of the government after a string of food and drug safety scandals over the past decade.
Hundreds of thousands of people impacted
Last week, the China Food and Drug Administration said Changsheng had doctored production and product inspection records for a rabies vaccine. The regulator also identified other problems with processes and equipment.
Although the problematic rabies vaccine had not been shipped out, Changsheng admitted to selling 250,000 doses of a vaccine for diphtheria, tetanus and pertussis (whooping cough) to Shandong province last year.
Authorities have ordered all production stopped at Changsheng and a massive vaccine recall.
Meanwhile, police in the northeastern city of Changchun said Monday they had taken in the company chairwoman and four other executives as part of a criminal investigation.
Separately, authorities in Hebei province near Beijing announced on Monday that nearly 150,000 people had received a substandard diphtheria, tetanus and pertussis vaccine made by another firm, Wuhan Institute of Biological Products.
The scandals caused pharmaceutical companies to plunge on the stock market.
Government vows harsh response
Authorities and state media have sought to take control of the narrative after the issue of lax regulation and food and drug safety went viral on social media.
Chinese President Xi Jinping, traveling in Africa, chimed in Monday, calling Changsheng's illegal production of vaccines "vile" and "shocking," according to state broadcaster CCTV.
Premier Li Keqiang had earlier called for an investigation and severe punishment for any criminality.
"We will resolutely crack down on illegal and criminal acts that endanger the safety of peoples' lives, resolutely punish lawbreakers according to the law, and resolutely and severely criticize dereliction of duty in supervision," he said.
The state-run China Daily called on the government to be "transparent" in handing the scandal. The Communist Party-tied Global Times urged authorities to "follow up on people's security demands, and supervise and regulate more effectively."
On social media, users were enraged.
"All my friends are freaking out with this vaccine case, everyone is scared. It really reflects big loopholes and issues with China's food and drug safety regulation," wrote one Weibo user under the handle 1988 Cheng Hongyu.
cw/tj (AFP, AP, dpa, Reuters)