The operation came amid concerns that some health centres were claiming to offer the WT1 vaccine as a way to prevent certain types of cancers.
Speaking on an RTHK radio programme, Chan said authorities had not found any WT1 jabs during the raids, nor discovered anyone who had received it.
Among the items seized, he said, were some 20 types of suspected unregistered jabs, with most of them being vitamins and amino acid health injections.
Chan warned that people could put their lives at risks if they get the unregistered WT1 vaccine.
“Because this is an injectable. We are very worried that during manufacturing or the administration of the injection, there may be a bacterial infection, posing risks to the recipient,” he said.
“Mild bacterial infection could lead to fever and inflammation, but severe ones could result in organ damage or even death.”
Chan said investigations showed that a local company had supplied WT1 reagents to some medical centres.
He went on to say that the reagents were labelled for research purpose only, and not for human use.
It is believed that the local firm obtained the reagents from overseas, he added.
Chan urged the public not to trust relevant advertisements easily, while health authorities have required local health providers to take down the advertisements for the jab.
As relevant promotions often appeared on social media platforms on the mainland, Chan said the department had also notified mainland authorities to help remove them.
All medical advertisements are strictly regulated under the laws in Hong Kong, Chan added, and authorities would take strict enforcement actions if they discovered any false advertising.