Hong Kong's Department of Health said on August 31 that it is following up seriously on media reports that some medical centres were offering a vaccine called WT1, claimed to prevent multiple types of cancer. The department said the vaccine is not a registered pharmaceutical product in Hong Kong, and advertising it for cancer prevention is a misleading claim. It carried out further unannounced inspections of seven premises across Hong Kong and Kowloon, including HK Pacific Asia Medical Centre, after receiving reports in July about the centre and affiliated organisations promoting the vaccine on social media.

The department said it had notified Mainland authorities and local law enforcement, including the Customs and Excise Department, and referred the case to the Medical Council of Hong Kong over registered doctors' professional conduct. It said it found no registration records for the vaccine with drug regulators in the Chinese Mainland or overseas, and warned that healthcare professionals who mislead patients about its cancer-preventing effects may cause delays in seeking treatment. Warning letters were issued over advertisements suspected of breaching the Undesirable Medical Advertisements Ordinance.

Illegal sale or possession of unregistered pharmaceutical products carries a maximum fine of $100,000 and two-years' imprisonment, while importing or exporting such products without a licence carries a maximum fine of $500,000 and two-years' imprisonment. From 2021 to June 2026, the department's Drug Office handled 138 cases involving convictions for sale or possession of unregistered pharmaceutical products.