Prenatal tetanus-diphtheria-acellular pertussis vaccine effectiveness at preventing infant pertussis

A study by the CDC and EIP Network evaluated the Tdap vaccine with five pertussis components (Tdap5) administered during pregnancy. The study, covering data from 2011 to 2014, found that when pregnant women received Tdap5 between 27 and 36 weeks of gestation, it was remarkably effective, with a 92.5% effectiveness in preventing pertussis in infants. However, the study couldn't assess protection against pertussis-related hospitalization due to a lack of differences between cases and controls. Importantly, Tdap5 vaccination after pregnancy or within 14 days before delivery did not offer the same level of protection for infants. This research underscores the vital role of Tdap5 vaccination during pregnancy in safeguarding young infants from pertussis.

Objective

To evaluate the effectiveness of the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine containing five pertussis components (Tdap5; Adacel^®, Sanofi) when given during pregnancy at preventing pertussis in infants less than 2 months of age.

Methods

The US Centers for Disease Control and Prevention (CDC), in collaboration with the Emerging Infections Program (EIP) Network, undertook a case-control study evaluating the effectiveness of Tdap vaccination in pregnancy against pertussis in infants less than 2 months of age based on data collected by the EIP Network from 2011 through 2014. The dataset from the CDC/EIP Network study was used to conduct this product-specific vaccine effectiveness analysis of Tdap5 vaccination in pregnancy to prevent disease in young infants. The main outcome of interest was vaccine effectiveness in infants whose pregnant parents were vaccinated with Tdap5 between 27 and 36 weeks' gestation, in accordance with the ideal timing for Tdap vaccination in pregnancy recommended by the US Advisory Committee on Immunization Practices. Odd ratios (ORs) and 95 % confidence intervals (CIs) were estimated using conditional logistic regression, and vaccine effectiveness was calculated as (1-OR) × 100 %.

Results

There were 160 infant pertussis cases and 302 matched controls included in this Tdap5-specific study. Tdap5 effectiveness in preventing pertussis in infants whose pregnant parents were vaccinated between 27 and 36 weeks' gestation was 92.5 % (95 % CI, 38.5 %-99.1 %). Effectiveness of Tdap5 against pertussis-related hospitalization in infants whose pregnant parents were vaccinated between 27 and 36 weeks' gestation could not be calculated due to lack of discordance among matched cases and controls. Vaccination of the parents after pregnancy or less than 14 days before delivery did not protect infants from pertussis.

Conclusion

Tdap5 vaccination in pregnancy between 27 and 36 weeks' gestation is highly effective at protecting young infants from pertussis.

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