Health reporter, BBC News
MMR vaccine provides immunity against measles
Babies exposed to measles should be injected with antibodies to temporarily boost their immunity, UK experts say.
The Health Protection Agency researchers also advise lowering the age at which the MMR vaccine can be given in an outbreak to six months.
Measles cases in England and Wales rose by 36% in 2008, largely among children not fully vaccinated with the MMR.
One expert at Great Ormond Street Hospital said measles was particularly dangerous in the very young.
Before the measles vaccine was introduced in 1968, very young babies had some temporary protection from antibodies passed from their mother in the late stages of pregnancy.
But because most mothers now have vaccine-mediated immunity rather than natural immunity against measles, that protection in babies is less than it was, the HPA researchers wrote in Archives of Diseases in Childhood.
By four to five months of age, only 25-45% of babies now have protective levels of measles antibody.
The researchers say because of this and the "worrying" increase in measles cases, babies who have been come in contact with someone with measles should receive an injection of human antibodies to give their immune systems a fighting chance.
This human normal immunoglobulin (HNIG) is made from donor plasma and is currently used in immuno-compromised patients, such as children with leukaemia.
It was also previously offered in outbreaks in infants older than six months but too young for the MMR.
The effects last a few weeks.
Public confidence in the triple MMR vaccine dipped following research - since discredited - which raised the possibility that the jab may be linked to an increased risk of autism.
Experts say MMR uptake needs to hit 95% for herd immunity but in England and Wales uptake of the first of the two vaccine courses is still only 85%.
A total of 1,348 cases of measles were reported last year - the highest figure since the monitoring scheme was introduced in 1995.
Wales is currently seeing a record number of cases and London has been particularly hit by outbreaks.
HPA immunisation expert Dr Mary Ramsay said the use of HNIG was well established.
"As measles is highly infectious, it's spreading easily among school aged unvaccinated children and we have measles outbreaks in schools.
"Cases have also filtered out to the general population.
"We know that in the first year of life, before the age of routine vaccination, measles can cause a severe illness with a high rate of complications."
Dr David Elliman, consultant community paediatrician at Great Ormond Street Hospital, welcomed the proposals.
"There is an argument, that if you are that worried about immunity, what about moving the age of routine immunisation down and people may want to think about that.
"The thing that powers this decision is if you get measles when you're very young it is a more serious disease."
He added that although MMR uptake was now starting to rise once more, measles outbreaks would be seen for quite some time.
"There are still a lot of children who are not immunised and they're now going through school - it is still a significant problem."