during the early months of life, according to Tami H. Skoff of the Centers for Disease Control and Prevention, Atlanta, and her associates.
In an analysis of 240 infants younger than 2 months with pertussis cough onset between 2011 and 2015 and 535 control infants, 57% of case mothers and 67% of control mothers had at least one valid Tdap dose; 13% of vaccinated case mothers and 14% of vaccinated control mothers had more than one valid dose of Tdap reported.
Of Tdap doses received during pregnancy in 22 cases and 117 controls, 77% were received during the third trimester, most during the Advisory Committee on Immunization Practices’ recommended 27-36 weeks of gestation. Of the Tdap doses received before pregnancy in mothers of 24 cases and 67 controls, 25% of the case mothers and 67% of the control mothers received Tdap 2 or fewer years before pregnancy.
The effectiveness of Tdap vaccination during the third trimester of pregnancy was 78%, and effectiveness during the first or second trimester was 64%. Effectiveness of Tdap given 2 or fewer years before pregnancy was 83%. This study was not powered to determine a difference if the vaccine was administered in the ACIP-recommended time period during the third trimester.
A reported 49% of U.S. pregnant women received Tdap during the 2015-2016 flu season, an increase of 22% from the 2013-2014 season, according to a CDC Internet panel survey.
“While maternal immunization during pregnancy will help bridge the gap until next-generation pertussis vaccines are licensed and available for use, this highly effective strategy will likely remain an integral component of pertussis prevention and control, even in the setting of new vaccines,” the investigators said.
Read more in Clinical Infectious Diseases (2017 Sep 28. doi:).