Background: In 2013, pertussis immunization (Tdap) for pregnant women was implemented in Colombia to protect newborns in response to increased pertussis incidence.
Objective: To assess the effect of Tdap maternal immunization on the concentration of mother/umbilical cord antibodies and the occurrence of pertussis in infants during their first six months of life.
Methods: A cohort study in eight randomly selected hospitals in Medellin and metropolitan area of Antioquia, Colombia was conducted in 2015-2016. IgG PT antibody levels in paired maternal and umbilical cord sera were measured from 805 mothers immunized recruited during labor and 200 mothers recruited during the prenatal care before immunization and followed until delivery. Antibodies were analyzed by commercial ELISA kits. 896 infants were followed to detect acute respiratory infections and paroxysms of coughing, inspiratory whoop, apnea, cyanosis or post-tussive vomiting. For laboratory confirmation, B. pertussis- specific real time PCR was performed.
Results: We observed a high prevalence of titers >100 IU/mL (mother: 18.40% [95% CI 16-21%]; umbilical cord: 23.1% [95% CI 19.2-27.4%]), positive correlation of umbilical cord and maternal antibodies, higher antibody concentration in vaccinated than in non-vaccinated mothers and significant difference in antibody levels before and after vaccination (Wilcoxon test p = 0.000). The trans placental transport ratio was higher if the mother was vaccinated between 26 and 30 weeks of pregnancy and maximum eight weeks before delivery. Two cases of pertussis were confirmed in infants (incidence of 1.99 per 1000).
Conclusion: The expected effect of Tdap maternal vaccination against pertussis was observed.
Keywords: Colombia; Latin America; Pregnant; Seroepidemiological study; Vaccination; Whooping cough.
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