Tdap Vaccine During Pregnancy Reduces Newborn Pertussis

October 10, 2017 12:23 pm News Staff

A CDC study(academic.oup.com) published Sept. 28 in Clinical Infectious Diseases found that vaccinating pregnant women with the tetanus, diphtheria and acellular pertussis (Tdap) vaccine during their third trimester was nearly 78 percent effective in preventing pertussis in their infants younger than 2 months.  

[Health care professional holding syringe in front of pregnant woman's abdomen]

However, it's important to note that less than half of pregnant women who delivered infants in the United States between fall 2015 and spring 2016 received the Tdap vaccine. That figure clearly demonstrates an opportunity exists to improve Tdap vaccination rates in pregnant patients.

The CDC recommends pregnant patients receive Tdap vaccine(www.cdc.gov) during every pregnancy, preferably during the early part of gestational weeks 27 through 36, to protect infants from pertussis in their first months of life. Adhering to this vaccination timing results in the greatest transfer of protective antibodies from mother to infant. The AAFP agrees in its own recommendation.  

"Women have such a great opportunity to help protect their babies before they enter the world by getting Tdap vaccine while pregnant," said Nancy Messonnier, M.D., director of the CDC's National Center for Immunization and Respiratory Diseases, in a news release(www.cdc.gov). "This study highlights how babies can benefit when their mothers get the vaccine and reinforces the CDC's recommendation for women to get Tdap vaccine in the third trimester of each pregnancy."

Story highlights
  • A recent CDC study estimated that vaccinating pregnant women against pertussis during their third trimester was nearly 78 percent effective in preventing pertussis in their infants younger than 2 months.
  • Using case surveillance data from six U.S. Emerging Infection Program Network sites, researchers conducted a case-control evaluation involving pertussis cases in infants younger than 2 months who had cough onset between Jan. 1, 2011, and Dec. 31, 2014.
  • The population analyzed included 240 case infants and 535 control infants, with about 7 percent of case mothers and 17 percent of control mothers receiving Tdap during their third trimester of pregnancy.

Study Details

This study used case surveillance data from six U.S. Emerging Infection Program Network sites. Researchers conducted a case-control evaluation involving pertussis cases in infants younger than 2 months who had cough onset between Jan. 1, 2011, and Dec. 31, 2014. Provider-verified immunization history was collected for all mothers and infants.

The population analyzed included 240 case infants and 535 control infants, with about 7 percent of case mothers and 17 percent of control mothers receiving Tdap during their third trimester of pregnancy.

Mothers were considered vaccinated during pregnancy if Tdap vaccine was given 14 days or more before delivery; trimester was calculated using Tdap date, infant's date of birth and gestational age.

Disease Severity

According to the CDC, infants younger than 1 year are at the highest risk for severe complications or death from pertussis.

"Typically, between five and 15 babies die from whooping cough each year in the United States; most deaths are in those too young to be protected by getting their own whooping cough vaccines," the news release noted. "Babies do not get vaccinated to start building their own protection against whooping cough until they are 2 months old."

In this study, 65 percent of infants younger than 2 months who were diagnosed with pertussis required hospitalization for treatment. It seems especially fortuitous, then, that the study found Tdap vaccination during the third trimester was estimated to be more than 90 percent effective in preventing serious cases of pertussis that required hospitalization.

Vaccine History

Before the pertussis vaccine was introduced in the 1940s, more than 200,000 cases of the disease were reported in the United States each year, said the CDC. After the vaccine entered the market, pertussis cases dropped to fewer than 10,000 by 1965 and bottomed out in 1976 at slightly more than 1,000 cases.

Starting in the 1980s, however, pertussis cases started to rise again -- though not to pre-vaccine levels -- with a peak of more than 48,000 cases in 2012.

That year, the CDC began recommending women get a pertussis vaccination during each pregnancy. Since that recommendation was made, pertussis cases have dropped again.

So far in 2017, more than 11,000 cases of pertussis have been reported to the CDC.

Mounting Evidence

The CDC's study provides another piece of evidence supporting Tdap vaccination during pregnancy(www.cdc.gov) to prevent pertussis in infants younger than 2 months.

Among the research supporting maternal vaccination with Tdap, five additional studies -- three from the United Kingdom and two in the United Sates -- found much lower rates of pertussis in infants after their mothers received Tdap vaccination during pregnancy.

Another U.S. study found that infants diagnosed with pertussis whose mothers received the Tdap vaccine during pregnancy were significantly less likely to be hospitalized, said the CDC news release.

Related AAFP News Coverage
Fresh Perspectives: Disease Outbreak Shows What -- and Why -- We Can Learn From Mistakes
(5/16/2017)

Confluence of Factors Contribute to California's Worsening Pertussis Outbreak
(12/31/2014)

Pertussis Is Latest Disease Outbreak Concern in United States
FP Offers Advice on Reinforcing Need for Immunization
(6/25/2014)

More From AAFP
Familydoctor.org: Whooping Cough(familydoctor.org)

Additional Resource
CDC: Pregnancy and Whooping Cough: Vaccinating Pregnant Patients(www.cdc.gov)