Researchers have found that natural protection against the disease passed down from their mothers only lasts between one and four months, leaving a window of vulnerability until they are vaccinated at a year old.
Now they are recommending that doctors should consider giving the measles, mumps and rubella vaccine earlier especially if it is known there is an outbreak of the potentially fatal disease.
Dr Elke Leuridan, of the University of Antwerp, Belgium, and colleagues said their findings underline the importance of measles vaccination around a child's first birthday and support ongoing research into earlier vaccination.
"This study describes a very early susceptibility to measles in both infants of vaccinated women and women with naturally acquired immunity," they said.
"If future studies show measles vaccines can be offered with success at an age of less than nine months, policy-makers could consider moving forward the routine measles vaccination programme."
The study, published in the British Medical Journal, involved 207 healthy women and their babies recruited from five hospitals in Antwerp.
Medical records were analysed and the women divided into two groups – those who were vaccinated against measles as children, and those who had acquired immunity from catching measles.
Levels of measles antibodies were measured from blood samples taken during week 36 of pregnancy, at birth (from umbilical cord blood), and in all babies when they were one, three and 12 months old.
The babies were also randomly tested at either six or nine months.
Results showed that vaccinated women had far fewer antibodies than women who were naturally immune.
The babies of vaccinated women also had significantly lower antibody levels than those of naturally immune women.
In the group of babies, maternal antibodies typically lasted for 2.61 months on average.
The figure was 3.78 months for infants of naturally immune women and 0.97 months for babies of vaccinated women.
At six months old, more than 99 per cent of babies of vaccinated women and 95% of babies of naturally immune women had lost the protection from their mother's antibodies.
Aged nine and 12 months, no babies had any levels of protection.
The MMR jab is given in two doses to ensure immunity. The most recent figures show 92.1 per cent of youngsters have had their first dose of MMR but only 83.2 per cent have had their second.
Uptake is therefore below the 95 per cent level recommended by the World Health Organisation to prevent outbreaks of disease.
In 1996, two years before MMR was linked to autism in controversial medical research, there were just 112 cases of measles in England and Wales.
By 2008 this figure had jumped to 1,370, and to 1,144 cases in 2009.
In the latest study, breastfeeding, birth weight, educational level of mothers and whether the babies were in day care or had been delivered by Caesarean had no significant impact on the results.
The researchers found no significant impact of breastfeeding, birth weight, educational level, caesarean section or day care attendance on the duration of maternal antibodies.
They suggested that at the moment early vaccination should be considered during an outbreak or after contact with siblings with measles, and for infants travelling or migrating to endemic areas.
"Most importantly, we confirm the extreme importance of timely administration of the first dose of measles vaccine," they added.
(c) The Telegraph Group