The government's free vaccines for newborn babies are highly unlikely to make them ill, although there can be occasional side effects, the Public Health Ministry insisted on Monday.
Supakit Sirilak, the ministry's deputy permanent secretary, made the statement after a group of families from Lop Buri, Kanchanaburi, Roi Et and Nonthaburi provinces lodged complaints with the ministry over illnesses their children had suffered, which they blamed on the vaccinations.
The group was accompanied by Pavena Hongsakula, chairwoman of the Pavena Foundation for Children and Women, who said the foundation is monitoring the cases closely.
The parents said their babies all suffered from weak muscles in their left legs after receiving the oral polio vaccination and the combined vaccination injection for diphtheria, whooping cough and tetanus jab at local hospitals.
A two-month-old toddler, one of the four cases, in Lop Buri, died after receiving the free vaccinations last month, the group claimed.
Dr Supakit said the ministry has not ignored these cases, but pledged that he would forward them to the ministry's special committees, one looking into the muscle complaint and another studying general side-effects of vaccinations.
"These panels have received many complaints about these symptoms [weak leg muscles] each year," he said.
He insisted that to the best of his knowledge the death of the two-month-old was not related to vaccinations as a medical report showed that she died from a lung infection.
Meanwhile, he said that the ministry has forwarded a case of a six-month-old female baby from Kanchanaburi who became weak after receiving the free-vaccination package at the age of two months to the two special committees of the ministry to help analyse the case, saying that the oral polio vaccination could have caused her side-effects.
"There is always a chance that one in about five million people might become sick due to the oral polio vaccination, but the benefits outweigh the risks," he said, adding that physical rehabilitation should improve the child's condition.
The ministry said the universal healthcare package will cover both compensation and treatment for this case.
He said the ministry may consider moving away from the oral polio vaccination as the injection appears to carry less risk of side-effects, although it is more expensive.
Chian Sodaphan, a 42-year-old father of the six-month-old toddler from Kanchanaburi, said he was satisfied with the ministry's action even though no-one could prove if it was the vaccination that had caused his daughter's leg complaint.
According to the ministry, around 700,000 newborn babies per year receive 2.1 million oral doses of the polio vaccine between them.
The last case of polio reported in the country was back in 1997.