BEIJING — Apple Zhou doesn’t trust Chinese vaccines.

She took her 2-year-old son to Hong Kong to get an imported tetanus shot, a trip that cost $3,000 — and she will do it again the next time he needs any preventive treatment.

But after a pair of China’s biggest vaccine makers acknowledged this month selling mislabeled and faulty medications, Zhou’s just-to-be-safe attitude chilled into fear.

“I was thinking about having a second child,” she said, “and now I’m beginning to hesitate.”

In a country that manufactures 95 percent of its vaccines, parents are increasingly looking outside the mainland to get imported medicines. Poorer families, meanwhile, are left wondering whether they can trust the shots at local clinics. 

Public confidence in the country’s $4.4 billion vaccine industry took a blow on July 15, when government inspectors reported that Changchun Changsheng Biotechnology had sold more than 250,000 defective vaccines meant to protect children against diphtheria, whooping cough and tetanus. 

The company also faked inspection reports, authorities found. 

Then on Tuesday, China’s drug watchdog announced that another company, the state-owned Wuhan Institute of Biological Products, had also peddled ineffective vaccines. The company started recalling about 400,000 doses in May and must now pay an unspecified fine, the China Food and Drug Administration said. 

Hundreds of thousands of children are thought to have been injected with the useless medicine, officials said. So far, they appear unharmed, except for a prolonged vulnerability to otherwise preventable diseases. 

Chinese officials ordered the arrest of 18 people at Changchun Changsheng and vowed that anyone involved in deceitful or negligent enterprises would be banned from the pharmaceutical industry for life. 

President Xi Jinping, who has pledged to curb corruption in China’s food and drug industries, called the news “appalling” and launched an investigation into the health-care crisis.

The government’s crackdown on corporate misbehavior has not quelled concerns among parents.

Word of the debacle blazed across social media, despite efforts by censors to stop it. A related hashtag garnered more than 600 million hits. On Tuesday, photos showed people in Beijing protesting the mismanagement of vaccines. 

Jackie Li, an agent at Jie Cheng Consulting, which helps mainland clients book appointments with Hong Kong hospitals and clinics, said the backlash has boosted his business. Bookings at his firm have tripled in the past two weeks. 

“It’s mainly due to the concern of the safety of the vaccines,” he said.

A report published Tuesday by Xiaodoumiao, a Chinese app for booking vaccination appointments, said 36 percent of respondents in a survey of 300,000 parents said they would give their child a domestic vaccine, while 60 percent said they would consider seeking the treatment in other countries. 

“Now they believe that imported vaccines are safer,” the authors wrote. “It’s a huge challenge for domestic vaccines to rebuild confidence.”

Tao Lina, a vaccine analyst in Shanghai, said he expects to see parents flock to Hong Kong — where rules allow the import of vaccines from France and Britain — as well as to other areas.

“They think the vaccines there are more reliable,” he said. 

Luna Lin contributed to this report.