The case involves the illegal and improper storage, transport and sale of tens of millions of dollars' worth of vaccines -- many of them expired -- reports say.
It is the latest health and safety scandal to emerge in China, where 300,000 children fell ill, six of them dying, in a notorious 2008 case involving milk powder contaminated with melamine.
Public fury has erupted over authorities' delay in publicising the case, which only came to light this month despite the two key suspects, a mother and daughter from Shandong province in eastern China, being arrested in April 2015, almost a year ago.
The fact that "a large number of vaccines flowed for a long time through illegal channels without regulators promptly discovering it shows there are loopholes in our regulations", it cited him as saying.
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At the same press conference the deputy director of the ministry of public security said it was "thoroughly" investigating the case, it added.
The number of people held over the scandal had stood at 37 on Wednesday, according to reports. CCTV did not give details of the latest detentions.
They included shots for polio, rabies, hepatitis B and flu for both children and adults, Caijing magazine said, citing drug safety officials.