Authorities in China's Shandong province have uncovered a massive illegal vaccine ring, triggering protest from the residents.
Police arrested a former doctor and her daughter in a case involving $88 million worth of improperly refrigerated vaccines.
China's state news agency Xinhua said the potentially compromised vaccines could cause disability and death.
Anger among citizens flared up when reports surfaced that a boy had died after being administered with a vaccine from this lot. However, authorities claimed the death was unrelated to the vaccine scandal.
The two women arrested in the case had bought vaccines from licensed and unlicensed sources and sold them to local health centers at high prices. The illegal products included 12 vaccines, 2 immune globulin and one therapeutic product.
The vaccines were produced by qualified manufacturers, but they were not transported in approved conditions, Xinhua said.
Police hunt 300 more
Shandong authorities said almost two million doses of the spurious vaccines were sold across 24 provinces. They included vaccines for rabies, polio, meningitis, hepatitis B and mumps.
Furious residents took to Weibo to express their anger.
"This is such a huge case and not a single regulatory official has come out to apologise, not a single one has resigned... this system which doesn't care whether ordinary citizens live or die makes one's soul tired," said one user, according to China Digital Times.
"24 provinces, 5 years already, and how many children!... It's been nearly a year and then they reveal this! Isn't this genocide? Words cannot express how angry I am!" wrote another.
Following the arrest of the ring leaders, China's drug regulator and police are searching for 300 suspects across the country.