The British government has strongly rejected what it describes as "media hysteria" over the MMR triple vaccine and said lives would be at risk if the number of children getting vaccinated declines.
Mr Blair's official spokesman said all medical experts are united in saying MMR is the safest choice.
The reassurance comes after eight more cases of measles were confirmed at an outbreak in south London.
He hit out at MMR being used "as part of the general political football".
The spokesman categorically denied reports that Prime Minister Tony Blair has ordered a review of the costs of offering single vaccinations as an alternative to the triple jab.
The evidence on vaccinations was always kept under constant review but all the scientific research pointed to the triple MMR jab, which had been given in 500 million doses in 90 countries, the spokesman said.
"Medical opinion - not political opinion - is that separate injections would result in a low take-up and experience in Japan, where for a short period they had to introduce separate injections because of a production problem, underlines that.
"Take-up went down and children died from measles - that is a fact. People have to address the hard reality of what Japan showed.
"It is a question of what does the scientific community believe is the best way forward, and that is MMR."
PA