In findings published in Jama Pediatrics in February 2023 a CDC study revealed that the maternal Tdap (tetanus toxoid, reduced diptheria toxoid, and acellular pertussis) vaccine decreases incidence of pertussis in infants younger than 2 months. Infants younger than a year old have the “highest burden of pertussis morbidity and mortality”. Thus, the US introduced the Tdap vaccination during pregnancy in 2011, to protect infants before vaccinations begin.  

The study 

The ecologic study examined more than 57,000 cases reported in children under one year old between 2000 and 2019. Statistical analysis was performed between 2020 and 2022. The study was divided into two periods: the pre-maternal Tdap vaccination period (2000-2010) and the post-maternal vaccination period (2012-2019).  

A total of 57,460 cases were reported in infants younger than 1 year across both periods, with 19,322 of these occurring in infants under 2 months old. The authors note that in the pre-maternal Tdap vaccination period, incidence did not change among infants under 2 months, but decreased in the post-maternal Tdap vaccination period for infants under 2 months.  

There were about 165 cases per 100,000 infants under 2 months each year before maternal vaccination was introduced. During the vaccination period, average cases dropped to 122 per 100,000. Further into the post-maternal vaccination period, from 2017-2019, this fell to 81 per 100,000. However, the authors note that there was not a similar decrease in cases among children between 6 and 11 months old, who were not dependent on maternal vaccination.  

Safe and effective 

Dr Linda Eckert, American College of Obstetricians and Gynaecologists’ liaison to the CDC encourages “everyone who is pregnant” to “feel confident in knowing that the Tdap vaccine is safe and effective”.  

“Knowing that Tdap vaccination during pregnancy protects nine in ten babies from being hospitalised with whooping cough, I strongly recommend this vaccine to all my pregnant patients for the peace of mind and for their family’s health and well-being.”  

Dr José Romero, Director of the CDC’s National Centre for Immunisation and Respiratory Diseases, said that this vaccine “offers infants the best protection before they are old enough to receive their whooping cough vaccines”.  

“This protection is critical because those first few months are when infants are most likely to have serious complications, be hospitalised, or die if they get whooping cough.”  

A plateau in vaccination 

Although the CDC recommends that pregnant patients take the vaccine, only around 55% did in 2019. This “plateau” is attributed to poor health communication by Dr Suellen Hopfer of the University of California-Irvine.  

“The most credible and obvious and straightforward channels are the paediatricians and physicians, but I think we just need to do a better job at disseminating and prioritising this information through pharmacies, through social media”.  

Another issue might be access, suggests Dr Elizabeth Cilenti of Georgetown University. Speaking to Healthline, she indicated that “not all obstetricians’ offices administer the vaccine”, which could “make things more difficult”.  

For more discussion around encouraging vaccine uptake in maternal populations, come to the World Vaccine Congress in Washington this April.