Maternal Pertussis Vaccination, Infant Immunization, and Risk of Pertussis

Area of Science:

• Immunology
• Public Health
• Epidemiology

Background:

• Pertussis, or whooping cough, poses a significant risk to infants.
• Maternal pertussis vaccination programs aim to protect newborns before they can be vaccinated.
• The effectiveness of maternal vaccination and its impact on infant vaccination schedules require ongoing evaluation.

Purpose of the Study:

• To estimate the vaccine effectiveness (VE) of maternal pertussis vaccination.
• To determine if maternal vaccination influences the effectiveness of infant pertussis vaccination series.
• To analyze VE trends over time and by infant age.

Main Methods:

• A population-based cohort study utilized administrative health records from 279,418 mother-infant pairs across three Australian jurisdictions.
• Infants were classified as maternally vaccinated if their mothers received the pertussis vaccine at least 14 days before delivery.
• Pertussis infections in infants were identified through notifiable disease records, and VE was calculated using Cox proportional hazard models.

Main Results:

• Maternal pertussis vaccination demonstrated significant VE, decreasing from 70.4% in infants under two months to 43.3% in infants aged 7-8 months.
• VE was not statistically significant beyond eight months of age.
• While the third infant dose of pertussis vaccine showed slightly lower VE estimates in maternally vaccinated infants (76.5% vs. 92.9%), this did not correlate with increased pertussis infection rates.

Conclusions:

• Maternal pertussis vaccination administered around 28 weeks of gestation is associated with a reduced risk of infant pertussis infection up to eight months of age.
• Despite a potential slight reduction in infant vaccine effectiveness, maternal vaccination does not appear to increase the overall risk of pertussis disease in infants.