Specific antibodies against vaccine-preventable infections: a mother–infant cohort study

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Abstract
Objectives: To determine maternal and neonatal specific antibody levels to selected vaccine-preventable infections (pertussis, Haemophilus influenzae type b (Hib), tetanus and pneumococcus). Design: Prospective cohort study. Setting: A UK secondary care maternity unit (March 2011–January 2012). Participants: Mothers and infants within 72 h of delivery were eligible. Unwell individuals, mothers less than 18 years of age, and infants born at less than 36 weeks gestation, or weighing less than 2500 g, were excluded. HIV-infected mothers were included. 112 mother–infant pairs were recruited. Samples from 111 mothers and 109 infants (108 pairs) were available for analysis. Outcome measures: Specific antibody levels were determined using standard commercial ELISAs. Specific antibody to pertussis antigens (PT and FHA) of >50 IU/ml, defined as ‘positive’ by the test manufacturer, were interpreted as protective. Antitetanus antibody titres >0.1 IU/ml and anti-Hib antibody titres >1 mg/l were regarded as protective. Results: Only 17% (19/111) of women exhibited a protective antibody response against pertussis. 50% (56/111) of women had levels of antibody protective against Hib and 79% (88/111) against tetanus. There was a strong positive correlation between maternal-specific and infant-specific antibodies’ responses against pertussis (r s =0.71, ps =0.80, ps =0.90, ps =0.85, p<0.001). Only 30% (33/109) and 42% (46/109) of infants showed a protective antibody response to pertussis and Hib, respectively. Placental transfer (infant:mother ratio) of specific IgG to pertussis, Hib, pneumococcus and tetanus was significantly reduced from HIV-infected mothers to their HIV-exposed, uninfected infants (n=12 pairs) compared with HIV-uninfected mothers with HIV-unexposed infants (n=96 pairs) by 58% (<0.001), 61% (<0.001), 28% (p=0.034) and 32% (p=0.035), respectively. Conclusions: Low baseline antibody levels against pertussis in this cohort suggest the recently implemented UK maternal pertussis immunisation programme has potential to be effective.
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