|Our data demonstrated the effectiveness of anti-pertussis antibodies in bacterial pathogenesis neutralization, emphasizing the importance of placental transfer and breast-feeding in protecting infants against respiratory infections caused by Bordetella pertussis.
I have not read this article in full, only the abstract. It has just been published and the fulltext is not available for free.
On the duration of immunity to pertussis, if you had pertussis, your immunity is likely to be strong for 4-20 years. (the vaccine 'works' for 4-12 years). You could have had a subsequent infection that you were not aware of that boosted your immunity. Pertussis is endemic, making this likely.
|A review of the published data on duration of immunity reveals estimates that infection-acquired immunity against pertussis disease wanes after 4-20 years and protective immunity after vaccination wanes after 4-12 years.
Immunity to pertussis is not well understood. The vaccine triggers an immune response to the antigen presented in the vaccine and antibodies are produced. However, antibodies from the vaccine are not the only factor when it comes to clearing the pertussis bacteria. Immunity in the mucosal linings of the lungs also has a role to play, and this role is still poorly understood.
I suspect that it is a combination of immunity passed across the placenta and the immunity in colostrum and breast milk that together offer protection, in the way of passive immunity from the mother to the baby.