Early waning of maternal measles antibodies in era of measles elimination: longitudinal study

Tuesday, 26th of November 2013

[source]BMJ[|source]

International differences in the prevalence of maternal measles antibodies in infants have been described by Leuridan E (2003) and Caceres VM (2000). There also evidence that suggests that infants of vaccinated women have lower starting concentrations at birth and faster decay of measles antibodies. As more countries implement universal measles immunization of infants at the age of 12-15 months through routine or SIAs, the possibility of increasing gap of susceptibility due to the early loss of maternal antibodies may become important.

In this article, the authors investigated the duration of the presence of maternal antibodies to measles in infants on the basis of measurement at seven time points (a longitudinal study). The study documents that the proportion of immune infants of naturally immune women starts higher and finally reaches the proportion immune for the infants of vaccinated women after seven months. At 6 months of age, more than 99% in the vaccinated group and 95% in the naturally immune group had lost immunity. The report concludes that there is increasingly early susceptibility to measles both in vaccinated and unvaccinated. Calling on all countries to monitor their population susceptibility profiles as one of the risk factors for the outbreaks observed in recent pat.  More details on this technical update are available at:  http://www.bmj.com/content/340/bmj.c1626?view=long&pmid=20483946

 

Abstract

Objective: To investigate the duration of the presence of maternal antibodies to measles in infants.

Design: Prospective study (May 2006 to November 2008).

Setting: Five hospitals in the Province of Antwerp, Belgium.

Participants: Of 221 pregnant women recruited, 207 healthy woman-infant pairs were included—divided into a vaccinated group (n=87) and naturally immune group (n=120), according to vaccination documents and history.

Main outcome measure: Measles IgG antibodies measured by enzyme linked immunosorbent assay (ELISA) at seven time points (week 36 of pregnancy, birth (cord), and 1, 6, 9, and 12 months); decay of maternal antibody in infants modelled with linear mixed models.

Results: Vaccinated women had significantly fewer IgG antibodies (geometric mean titre 779 (95% confidence interval 581 to 1045) mIU/ml) than did naturally immune women (2687 (2126 to 3373) mIU/ml) (P<0.001). Maternal values were highly correlated with neonatal values (r=0.93 at birth). Infants of vaccinated women had significantly lower antibody concentrations than did infants of naturally immune women (P<0.001 at all ages over the follow-up period). Presence of maternal antibodies endured for a median of 2.61 months—3.78 months for infants of naturally infected women and 0.97 months for infants of vaccinated women. At 6 months of age, more than 99% of infants of vaccinated women and 95% of infants of naturally immune women had lost maternal antibodies according to the model.

Conclusions: This study describes a very early susceptibility to measles in infants of both vaccinated women and women with naturally acquired immunity. This finding is important in view of recent outbreaks and is an argument for timeliness of the first dose of a measles vaccine and vaccination of travelling or migrating children under the age of 1 year.