Effectiveness of Maternal Immunization With Boostrix at Preventing Pertussis Among Infants <2 Months Old in the United States

Study Overview
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Brief Summary
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The purpose of this study is to estimate the effectiveness of maternal immunization with Boostrix at preventing pertussis in infants in the United States.

Official Title
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Effectiveness of Maternal Immunization With Boostrix at Preventing Pertussis Among Infants <2 Months Old in the United States: Analysis of a Dataset From a Case-control Study

Conditions
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Whooping Cough

Intervention / Treatment
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* Other: Not applicable / dataset analysis


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Inclusion criteria for case infants: Case infants were eligible for the enrolment if they: were at least 2 days old and < 2 months old on the cough onset date resided in the catchment area on their cough onset date were born in a hospital in their state of residence were ≥37 weeks' gestational age at birth were neither adopted nor in foster care did not live in a residential care facility Inclusion criteria for control infants: Control infants were eligible for the enrolment if they: were at least 2 days old and <2 months old on the case infant's cough onset date were born in a hospital in their state of residence were ≥37 weeks' gestational age at birth were neither adopted nor in foster care did not live in a residential care facility were born at the same hospital as the case infant did not have pertussis diagnosis prior to the cough onset date of the corresponding case infant Exclusion Criteria: Infants (case and controls) whose mothers have received Adacel or mothers without brand information available, as well as controls who were matched to a case whose mother received Adacel or mothers without brand information available, will be excluded from the analysis of the effectiveness of vaccination with Boostrix.

Ages Eligible for Study
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Minimum Age: 2 Days
Maximum Age: 2 Months

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Pertussis Case Group<br>Infant subjects of at least 2 days old and less than (<) 2 months old, who met the pertussis diagnosis definition (laboratory confirmed pertussis, epidemiological linkage to a laboratory-confirmed case, clinically compatible illness), and who met the case infants inclusion criteria (resided in the catchment area on their cough onset date, were born in a hospital in their state of residence, had at least 37 weeks gestational age at birth, were neither adopted, nor in foster care and did not live in a residential care facility). This post-hoc analysis was limited to cases and controls whose mothers were either vaccinated with Boostrix or did not receive any Tdap vaccine. Cases with no remaining matched control were also excluded from the analysis and vice versa. | Other: Not applicable / dataset analysis<br>* Not applicable / dataset analysis<br>|
| Control Group<br>Infant subjects of at least 2 days old and less than (<) 2 months old, who did not have a pertussis diagnosis prior to the cough onset date and who met the inclusion criteria for control infants (were born on a hospital in their state of residence, were at least 37 weeks gestational age at birth, were neither adopted, nor in foster care, did not live in a residential care facility, were born at the same hospital as the case infant). This post-hoc analysis was limited to cases and controls whose mothers were either vaccinated with Boostrix or did not receive any Tdap vaccine. Cases with no remaining matched control were also excluded from the analysis and vice versa. | Other: Not applicable / dataset analysis<br>* Not applicable / dataset analysis<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Pertussis Cases and Matched Controls Among Infants Born to Mothers Vaccinated With Boostrix Vaccine (During Third Trimester of Pregnancy) or Not Exposed to Any Tdap Vaccine During Pregnancy | Vaccine effectiveness at preventing pertussis occurrence in infants < 2 months old is assessed by comparing the Boostrix immunization status during the third pregnancy trimester in mothers of infant pertussis cases and matched controls. The association between maternal Boostrix vaccination and pertussis in infants was analyzed using conditional logistic regression. The multivariate analysis was performed to obtain the adjusted values. Covariates that were statistically significant in the univariate analysis or considered as clinically significant were included in the multivariable conditional logistic regression model. Subjects with missing or unknown values, if any, for at least one of the risk factors were excluded from the model. | During the data collection period (from 1 January 2011 to 31 December 2014) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Pertussis Cases and Matched Controls Among Infants Born to Mothers Vaccinated With Boostrix Vaccine (Before Pregnancy, During First or Second Trimester, After Pregnancy) or Not Exposed to Any Tdap Vaccine During Pregnancy | Vaccine effectiveness at preventing pertussis occurrence in infants < 2 months old is assessed by comparing the Boostrix immunization status before pregnancy, during first or second pregnancy trimester, after pregnancy in mothers of infant pertussis cases and matched controls. The association between maternal Boostrix vaccination and pertussis in infants was analyzed using conditional logistic regression. The multivariate analysis was performed to obtain the adjusted values. Covariates that were statistically significant in the univariate analysis or considered as clinically significant were included in the multivariable conditional logistic regression model. Subjects with missing or unknown values, if any, for at least one of the risk factors were excluded from the model. | During the data collection period (from 1 January 2011 to 31 December 2014) | 
| Number of Pertussis Cases and Matched Controls Among Infants Born to Mothers Vaccinated With Boostrix Vaccine (During First, Second or Third Trimester) or Not Exposed to Any Tdap Vaccine During Pregnancy | Vaccine effectiveness at preventing pertussis occurrence in infants < 2 months old is assessed by comparing the Boostrix immunization status during pregnancy in mothers of infant pertussis cases and matched controls. The association between maternal Boostrix vaccination and pertussis in infants was analyzed using conditional logistic regression. The multivariate analysis was performed to obtain the adjusted values. Covariates that were statistically significant in the univariate analysis or considered as clinically significant were included in the multivariable conditional logistic regression model. Subjects with missing or unknown values, if any, for at least one of the risk factors were excluded from the model. | During the data collection period (from 1 January 2011 to 31 December 2014) | 
| Number of Pertussis Cases Leading to Hospitalization and Matched Controls in Infants Born to Mothers Vaccinated With Boostrix (Before Pregnancy, During First or Second, Third Trimester, After Pregnancy) or Not Exposed to Any Tdap Vaccine During Pregnancy | Vaccine effectiveness at preventing pertussis occurrence leading to hospitalization in infants < 2 months old is assessed by comparing the Boostrix immunization status before pregnancy, during first or second, third trimester, after pregnancy in mothers of infant pertussis cases and matched controls. The association between maternal Boostrix vaccination and pertussis in infants was analyzed using conditional logistic regression. The multivariate analysis was performed to obtain the adjusted values. Covariates that were statistically significant in the univariate analysis or considered as clinically significant were included in the multivariable conditional logistic regression model. Subjects with missing or unknown values, if any, for at least one of the risk factors were excluded from the model. | During the data collection period (from 1 January 2011 to 31 December 2014) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Whooping Cough, Boostrix, Tdap, effectiveness, pregnancy, infants