A recent study found that the introduction of maternal tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccination in 2011 was associated with a significant reduction in pertussis incidence among US infants younger than 2 months.
The ecologic study analyzed data from the National Notifiable Diseases Surveillance System, which included 57,460 pertussis cases reported in infants younger than 1 year from 2000 to 2019. Researchers compared incidence rates between the pre-vaccination (2000-2010) and post-vaccination (2012-2019) periods for infants younger than 2 months and those aged 6 to 12 months.
During the pre-maternal tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination period, the mean annual pertussis incidence among infants younger than 2 months was 165.3 per 100,000 infants. Following the introduction of maternal Tdap vaccination in 2011, the annual incidence rate of pertussis among infants younger than 2 months decreased to a mean of 121.8 per 100,000 infants during the post-maternal Tdap vaccination period. Among infants aged 6 months to less than 12 months, the mean annual pertussis incidence was 19.7 per 100,000 infants during the pre-maternal Tdap vaccination period, and no significant change in pertussis incidence was observed in this age group during the post-maternal Tdap vaccination period.
The study, published in JAMA Pediatrics, found that the difference in pertussis incidence between infants younger than 2 months and those aged 6 months to less than 12 months significantly decreased during the post-maternal Tdap vaccination period. The findings suggest an association between maternal Tdap vaccination and lower pertussis rates in infants under 2 months, with the potential for further reduction as vaccine coverage increases.
The researchers conducted sensitivity analyses to ensure the robustness of the data, using infants aged 2 months to less than 12 months and children aged 1 to 6 years as comparison groups in one analysis and not excluding the year 2011 from the model in another analysis.
The study had some limitations, including the lack of maternal vaccination status at the individual level in the surveillance data and the inability to determine with certainty the proportion of infants younger than 2 months who received pertussis vaccines prior to 8 weeks of age due to incomplete or missing vaccination history data in the National Notifiable Diseases Surveillance System.
The authors suggest that further reductions in infant pertussis incidence might be achieved if a higher proportion of pregnant women are vaccinated. They emphasize the importance of increasing Tdap vaccination uptake through education of prenatal care practitioners and other key practitioners who may routinely interact with pregnant women in their practices, such as pediatricians and family practice physicians.
The authors reported no potential conflicts of interest.