VE of Maternal Tdap and Infant DTaP Vaccination in Preventing Pertussis in 148 981 Newborns in the Study Population Followed From Birth Until 2 and 12 Months of Age

2-mo Follow-up (Total Pertussis Cases = 17)12-mo Follow-up (Total Pertussis Cases = 103)
No. of Pertussis Cases (Rate per 100 000 Person-Years)VE, % (95% CI)PNo. of Pertussis Cases (Rate per 100 000 Person-Years)VE, % (95% CI)P
Timing of maternal Tdap vaccinationNo maternal TdapMaternal TdapNo maternal TdapMaternal Tdap
 During pregnancy (8+ days before birth)a15 (112.7)1 (8.7)91.4 (19.5 to 99.1).03280 (109.1)22 (38.0)69.0 (43.6 to 82.9)<.001
 Before pregnancy15 (79.4)2 (32.5)68.6 (−44.9 to 93.2).13889 (89.4)14 (42.4)55.9 (20.7 to 75.5).006
 After pregnancy13 (59.3)4 (129.4)45.7 (−88.2 to 84.3).33680 (72.1)23 (106.2)24.4 (−27.8 to 55.3).296
Infant DTaP vaccination
 First dose48.2 (−6.4 to 74.8).073
 Second dose64.2 (17.9 to 84.4).015
 Third dose86.8 (69.2 to 94.4)<.001
  • —, not applicable to these analyses.

  • a VE of maternal Tdap vaccination during pregnancy was estimated from a Cox regression model, stratified on the year and month of birth of the infant and including covariates to adjust for sex, race, delivery hospital, maternal Tdap vaccination before and after pregnancy, and, for the 12-mo follow-up period, number of infant DTaP doses. Case counts do not include 1 infant, where maternal Tdap vaccination occurred 1 to 7 days before birth, because the VE estimate is based on comparing infants whose mothers received the Tdap vaccine during pregnancy at least 8 days before birth versus infants whose mothers had no Tdap vaccination during pregnancy. The VE estimate does not include infants whose mothers were vaccinated 1 to 7 days before birth as either vaccinated or unvaccinated during pregnancy; there were too few infants in this group to give a meaningful result, so the 1 case where this occurred is not included.