After several decades of vaccination against hepatitis B virus in newborns, infants, adolescents, and adults, the question remains whether a booster dose is ever needed. Long-term protection is most commonly measured through 4 methods: the anamnestic response after administration of a booster dose, infection rate in vaccinated populations, in vitro B and T cell activity testing, and seroepidemiological studies. Long-term protection is present despite a decrease in anti-hepatitis B surface antibodies over time. The exact mechanism of long-term protection, however, is not yet fully understood. There is no need for boosters in immunologically potent persons as long as a full course was adequately administered that respected the recommended timelines, as evidenced by studies conducted up to 20 years after the original immunization course. However, a booster dose should be planned for immunocompromised patients, based on serological monitoring.

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.

Vaccination during pregnancy has been recommended in some countries as a means to protect young infants from severe infection. Nevertheless, many aspects are still unknown and possible blunting of the infant's immune responses by maternal antibodies, is one of the concerns with maternal vaccination. We report the first prospective controlled cohort study in women and infants on the effects of using Boostrix(®), a combined tetanus, diphtheria and acellular pertussis vaccine, during pregnancy. The primary aim was to measure the influence of this booster dose on the titer and duration of the presence of maternal antibodies in the infants and assess possible interference with infant immune responses. In a controlled cohort study, 57 pregnant women were vaccinated with Tdap vaccine (Tetanus Diphtheria acellular Pertussis, Boostrix, GSK Biologicals), at a mean gestational age of 28.6 weeks. A control group of pregnant women (N=42) received no vaccine. Antibody geometric mean concentrations (GMCs) against tetanus (TT), diphtheria (DT), pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (Prn) were measured with commercial ELISA tests in samples taken preceding maternal vaccination and one month afterwards, at delivery and from the cord blood, and in infants before and 1 month after the primary series of 3 pertussis containing hexavalent vaccines. Infants born to vaccinated women had significantly higher GMC at birth and during the first 2 months of life for all vaccine antigens compared to the offspring of unvaccinated women, thereby closing the susceptibility gap for pertussis in infants. However, blunting was noticed for infant diphtheria and pertussis toxin vaccine responses (p<0.001) in the infants from vaccinated women after the primary vaccination schedule (weeks 8,12 and 16). Since pertussis vaccination has been recommended during pregnancy already, the results of this study support that recommendation and provide additional scientific evidence to document possible interference by maternal antibodies.

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