According to a commentary, the differences in initial and longer-term antibody responses to pertussis toxin between the vaccines containing the PTgen and the Tdap comparator vaccine are impressive, and larger than those found in the infant trials, but important questions remain.
• it is unclear whether the higher titres of antibody to pertussis toxin after vaccination with PTgen yield meaningful differences in protection.
• it is unknown whether performance will be similar in adolescents primed with acellular rather than whole-cell vaccines, as in Thailand.
• is there a clinical need for an acellular pertussis vaccine without diphtheria and tetanus toxoids?
It notes lack of a commercially available monovalent pertussis vaccine (without tetanus and diptheria toxoids) is cited by parents and providers as one barrier to high uptake of pertussis vaccination in pregnancy. It suggests that a monovalent pertussis vaccine containing PTgen that generates long-lasting high titres of pertussis toxin neutralising antibodies has the potential to improve protection against severe pertussis disease in neonates in the first 6 weeks of life. It might also reduce interference with immune responses to other antigens in the first 6 months of life, which seem to be primarily related to the presence of diphtheria and tetanus. It adds that such a vaccine could also be suitable for use in neonates whose mothers are not vaccinated.