By Patrick Yang ’20

Pertussis, more commonly known as whooping cough, is a life-threatening infection in infants that can easily be prevented through vaccination. However, infection rate has been increasing over the past several years. And since the DTaP vaccine for pertussis is administered after two, four, and six months of age, an infant is especially vulnerable during his or her first two months of life. As a result, maternal vaccination has been used to combat infection because antibody circulation in the mother can reach her unborn child through the placenta. The Advisory Committee on Immunization Practices (ACIP) has recommended Tdap vaccination, the adult version of the DTaP vaccination, for every pregnant woman.  Although maternal vaccination is widely practiced, its effectiveness against pertussis during an unborn baby’s initial two months is not well studied. This has given rise to arguments against maternal vaccination.

In response to criticism, Dr. Roger Baxter and fellow researchers at the Kaiser Permanente Vaccine Study Center in California observed the effectiveness of maternal Tdap vaccination during the first two months and year of life. Dr. Baxter’s study followed 148,981 infants born from 2010 to 2015. The study began on the day of birth and continued with follow-up periods at two months of age and one year of age. The mothers of 68,168 infants (45.8%) received the Tdap vaccination at least eight days before birth, whereas the other mothers were not vaccinated or vaccinated too close to birth to experience antibody transfer. By the end of the experiment, 17 infants contracted pertussis by two months of age, and 110 infants contracted pertussis by one year of age. Of the infected infants, only one of the 17 infants that were infected by two months of age had maternal Tdap vaccination, while 22 of the 110 infants that were infected by one year of age had maternal Tdap vaccination. As a result, maternal vaccine effectiveness before two months of age was found to be 91%, while vaccine effectiveness before one year of age was 69%.

This study provides evidence for effectiveness of maternal Tdap vaccination during the first two months of age. Interestingly, Tdap maternal vaccination does not interfere with the infant’s DTaP vaccination and continues to provide protection. The ACIP’s recommendations may now convince some critics that infants can be properly protected against lethal infections through maternal vaccination.

References:

1. R. Baxter, et al., Effectiveness of vaccination during pregnancy to prevent infant pertussis. Pediatrics 139, (2017). doi: 10.1542/peds.2016-4091.
2. Image retrieved from: https://www.flickr.com/photos/ryanboren/2899151607.