The use of smallpox vaccine to inoculate humans against monkeypox does not work, because it does not generate the immunity required to prevent monkeypox infection, according to Dr. Supakit Sirilak, director-general of the Medical Sciences Department, today (Monday).

He disclosed that the department recently conducted human trials on 30 volunteers, who were vaccinated against smallpox over four decades ago. The volunteers were divided into three age groups of ten each by age: 45-54, 55-64 and 65-74 years old.

Dr. Supakit said that the tests show that 28 of them did not develop any immunity against monkeypox and only two developed minimal level of immunity.

Citing the human trial results, he said that any decision to use the smallpox vaccine, which has been kept in the inventory of the Government Pharmaceutical Organisation (GPO), to inoculate humans against monkeypox must be weighed carefully as to whether it is worth the trial, because there has not been a case of smallpox infection for several decades and the risk of monkeypox infection is quite low except for close contact with the infected.

He also said that, to date, there is no monkeypox vaccine, but there is a new generation of smallpox vaccine, developed by the JYNNEOS Company in the United States and Europe.

The GPO has already procured about 1,000 doses of this vaccine, but any inoculations with this vaccine will depend on a committee, which will decide and set the guidelines for its use.

So far, only seven confirmed monkeypox cases have been detected in Thailand.