Measles: Gap in protection for young infants

19th May 2010 - Young infants appear to have a gap in their protection against measles. Belgian researchers have found that the immunity babies receive from their mothers wears off at around two to three months - but the measles jab (MMR) isn’t given until 13 months of age in the UK.

Antibodies which fight diseases are passed on by mothers whether or not they’ve been vaccinated, but these drop over time, leaving them susceptible until they are vaccinated.

The researchers say their findings underline the importance of measles vaccination at around 12 months and support ongoing research into earlier vaccination.

Measles cases are rising in the UK. In 2009 there were 1,143 cases in England and Wales compared with 70 in 2001. This drop is partly blamed on the now discredited MMR scare.

The study

The study involved 207 healthy women and infants from five hospitals around Antwerp, Belgium, from April 2006 and is published on bmj.com.

Researchers checked medical records and then divided the women into two groups: one that had been vaccinated against measles during infancy, and another that had a naturally acquired immunity from catching measles.

Measles antibodies were measured from blood samples taken during week 36 of pregnancy, at birth (cord blood), in all infants at one, three and 12 months, and randomly at either six or nine months.

The results

Measles vaccinated women had significantly fewer antibodies than those with natural immunity.

Infants of vaccinated women also had significantly lower antibody levels than infants of naturally immune women.

The maternal antibodies stayed with infants for around 2.6 to 3.8 months for infants of naturally immune women, but less than one month for infants of vaccinated women.

At six months, nearly all infants of vaccinated women and 95% of infants of naturally immune mothers had lost their maternal antibodies.

At nine and 12 months, no immunity remained in either group.

Maternal antibodies were not significantly affected by breastfeeding, birth weight, educational level, natural birth or caesarean delivery or attending nursery or day care.

Next steps

The researchers say that future studies would be needed to show whether measles vaccines could be safely offered before nine months.

One of the authors, Elke Leuridan, tells us by email: “First of all, infants’ immune systems work differently from adults’ immune systems. Although they react with less antibody production at younger ages, they do build up a memory immunity, which needs, however, to be boosted with another dose of vaccine in order to maintain protection.

“This means that with an early dose, at say six months, based on the evidence we now have, a booster is needed, apart from the recommended second dose against measles.”
That would mean children having three jabs for measles.