A US professor who led global efforts to eradicate smallpox, says new methods such as oral vaccine or skin patches are needed to overcome debates over the use of syringes for vaccinations.

Donald Henderson, emeritus dean of medicine at the Bloomberg School of Public Health at John Hopkins University in Maryland, said less "emotional" way than using syringes had to be discovered to ensure higher vaccination rates.

"If we could vaccinate with an oral vaccine, if we could vaccinate with a little patch on the skin, rather than the needle or syringe - which is an emotional thing with parents," he told AAP.

"We haven't done enough in the area, working on alternative ways to vaccinate which would be not so much of a problem, not so much of an emotional thing."

Prof Henderson, in Thailand to receive a prestigious Prince Mahidol Award in medical research, is internationally recognised in his efforts leading the World Health Organisation (WHO) team in the 1970s to eradicate smallpox.

Smallpox, one of the most devastating diseases of the 20th Century, claimed the lives of around 500 million people.

But success in eradicating and controlling viruses and disease has led to greater difficulties persuading people to get vaccinated, Prof Henderson said.

"The best thing you can do is try to do our best to persuade (people)," he said.

"Every parent has the right to say `my child - I don't want the child vaccinated'.

"And they have done that. And with this we have seen the total (vaccination) coverage fall from in some areas," he said.

Intensified debate in the US over vaccinations followed an outbreak of highly contagious measles earlier this year. The US Centre for Disease Control (CDC) reported that from January to April 10, 159 people in 18 states and District of Columbia were reported to have measles.

The CDC said the outbreak was largely concentrated in California (117 cases) when an unvaccinated Californian woman contracted the disease before travelling through airports and the Disneyland theme park.

The CDC said the measles virus was so contagious that 90 per cent of the people close to that person who were not immune would have become infected.

"If somebody wants to come into a country and doesn't want to be vaccinated, I don't think there's really much we can do. I think we would be getting into trouble if we try to mandate," Prof Henderson said.

Vaccines are a "very powerful tool and what we could use now is more research in certain areas, (such as) vaccines that are more easily taken," he said.