Vaccine Effectiveness

Pertussis vaccines are effective, but not long lasting. The good news is that infants are less likely to develop pertussis early in life if their mothers get the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine during pregnancy.

Tdap Effectiveness for Infant if Mother Vaccinated during Pregnancy

Evidence shows that young infants whose mothers got Tdap during pregnancy are less likely to develop pertussis during the first few critical months of life. A CDC evaluation found Tdap vaccination during the third trimester of pregnancy prevents 78% of pertussis cases in infants younger than 2 months of age. These findings are similar to other studies from the United Kingdom and the United States that suggest that vaccinating the mother during pregnancy is highly effective at protecting infants against pertussis.

When infants do get pertussis, their infection is less severe if their mother received Tdap during pregnancy. A CDC evaluation found maternal vaccination is 90% effective at preventing infant hospitalization from pertussis. Another U.S. study showed that infants whose mothers got Tdap during pregnancy had a significantly lower risk of hospitalization and intensive care admission and shorter hospital stays. That same study showed that no infants born to vaccinated mothers required intubation or died of pertussis.

Since pregnant women pass some protection to their infants through transplacental transfer of maternal antibodies, their infants also have some protection against the severe outcomes that come with this disease. It is critical that infants receive the 5-dose childhood DTaP series on schedule so they maintain protection throughout childhood.

DTaP Effectiveness for Infant if Mother Vaccinated with Tdap during Pregnancy

By vaccinating a woman with Tdap during pregnancy her infant will gain pertussis antibodies during the most vulnerable time — before 3 months of age. There is a theoretical concern that providing this early immunity may interfere with the infant’s immune response to DTaP though, resulting in a weakening of the infant’s immune response to DTaP. However, based on a recent study looking at this issue, this interference does not seem to cause any problems when it comes to protecting infants. Researchers are still working to better understand this issue.

The benefits of vaccinating during pregnancy and protecting a newborn outweigh the potential risk of blunting the infant’s response to DTaP. Since infants are at greatest risk of severe disease and death from pertussis before 3 months of age – when their immune systems are least developed – any protection that can be provided is critical. Infants should receive their DTaP vaccines on schedule, starting at 2 months of age.

See the Pregnancy and Whooping Cough Research page for a list of published articles specific to preventing pertussis in infants, including vaccine effectiveness studies.

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