The illegal vaccine ring was led by a mother and daughter from 2011 onwards, trafficking in expired vaccines made by licensed pharmaceutical companies for polio, rabies, chickenpox among others. The vaccines were worth $90 million, state media said.

The duo didn’t house the vaccines in proper temperatures, triggering fears they had lost their effectiveness.

The public outrage arrived quickly on Chinese social media.

“The place where everybody is vaccinated is a government department,” wrote one poster on Twitter equivalent Weibo.

“The government takes actions after everything is out of control,” said another. “It’s like all the boring Hong Kong films where police never appear until bad guys die.”

China’s state press was the first to report on the case last week. This week the country’s censors told the state press to avoid drawing attention to the story.

Why the news is only now rocketing around Chinese social media is one of the big unknowns.

State media said the mother and daughter were arrested last year.

On Sunday officials released the names of 300 people who purchased vaccines from them across 24 provinces in China—two-thirds of the country.

The World Health Organization in China downplayed the harm expired vaccines could cause, thought it highlighted the loss of efficacy.

“Vaccines need to be stored and managed properly or they can lose potency,” it said in a statement yesterday. “It is important to note, however, that improperly stored or expired vaccine seldom if ever causes a toxic reaction – therefore there is likely to be minimal safety risk in this particular situation.”

But that’s unlikely to be enough reassurance for China’s parents.

Well aware of the melamine-tainted milk scandal of 2008 that affected 300,000 babies and the spread of HIV through blood collection stations in the 1990s, the news story is expected to drag on until Friday, when local authorities are supposed to supply information on which hospitals purchased the vaccines.