Health authorities in Brazil started their annual polio vaccination program that this year will immunize 95 percent of the country's children under age five.
The 46-million-real (24-million-dollar) campaign will give anti-polio injections to 14.7 million children, with the second stage of the program to take place on August 22, the health ministry said in a statement.
Brazil stamped out polio in the 1980s after repeated vaccination campaigns.
"Now, the importance of the vaccine is to keep the country free of the virus that causes this illness. The shots don't have side-effects," the coordinator for the ministry's national immunization program, Maria Arindelita Arruda, said.
Poliomyelitis is a serious viral infection that in a minority of cases, particularly in children, can cause nerve damage and paralysis.
The World Health Organization is leading efforts to eradicate the disease entirely.
But it is still endemic in India, Pakistan, Nigeria and Afghanistan and several other countries, most in Africa, still struggle with the illness.
"The fact that polio is stamped out in Brazil is no reason for complacency," Arindelita said.
She added that the vaccination program would mean that "if someone brought in the virus from one of those countries, children won't run the risk of catching the disease."