Pertussis is a highly contagious infectious disease of the respiratory tract caused by Bordetella pertussis. Disease is most severe in young infants. In the USA, more than half of infants with pertussis require hospitalization when younger than 6 months and more than 80% when under 2 months old.^1,2 Prevention of infant pertussis is the main goal of pertussis vaccination strategies.³ Pertussis vaccination of pregnant women is safe and the most effective strategy to protect young infants against severe pertussis.^4–6 The main mechanism of passive protection in young infants is transplacental transfer of maternal antibodies against pertussis toxin (PT). PT released by B. pertussis during infection is responsible for severe disease and death in infants.^7–10 Maternal anti-PT antibody levels transferred to infants must be high enough at birth to maintain the capacity to neutralize toxin until infants have developed protective immunity through active childhood immunization.

All acellular pertussis vaccines including those used for vaccination in pregnancy contain PT that must be inactivated by chemical or genetic inactivation. The immunogenicity of PT is affected by the inactivation method. Chemical treatment affects the protein structure of PT, unlike detoxification by genetic engineering that maintains the conformational and immunological properties of native PT.^11–18 Consequently, vaccination with genetically detoxified PT (PT_gen) containing vaccines induces higher levels of anti-PT-neutralizing antibodies than vaccination with chemically detoxified vaccines.^19–23 Most pertussis vaccines used for vaccination in pregnancy have been chemically inactivated and are only available combined with tetanus and diphtheria (Tdap_chem).

A new generation recombinant pertussis booster vaccine was studied at multiple dose levels of PT_gen in a phase 2 randomized-controlled trial in pregnant women in Thailand.²³ Follow-up of mothers and infants at the time of birth confirmed active transplacental transfer of maternal anti-PT antibodies for all doses of recombinant pertussis vaccine that persisted at comparable or higher levels compared with Tdap_chem at 2 months of age.²⁴ We now report on safety and antibody responses to childhood vaccination with diphtheria-tetanus-whole cell pertussis (DTwP) and 13-valent pneumococcal conjugate vaccine (PCV13) in these infants until 13 months of age according to pertussis vaccine the mother received in pregnancy.