No association between influenza vaccination during pregnancy and adverse birth outcomes.

BACKGROUND: Pregnant women are recommended to receive inactivated influenza vaccination anytime during pregnancy. Studies have investigated the impact of influenza vaccination during pregnancy on birth outcomes and results on preterm birth have been inconsistent. METHODS: We conducted a retrospective cohort study among children born at a gestational age≥24weeks from January 1, 2010 to December 31, 2015 at Kaiser Permanente Northern California facilities (KPNC). We evaluated the association between maternal influenza vaccination during pregnancy and risk of preterm birth, small and large for gestational age, admission to the neonatal intensive care unit (NICU), respiratory distress syndrome, low birth weight, and low Apgar score. We ascertained the dates of maternal influenza vaccination, conception, and delivery, as well as birth outcomes from KPNC inpatient and outpatient databases. Conditional multivariate Cox regression and logistic regression analyses were used to determine the association between maternal vaccination during pregnancy and risk of each birth outcome. RESULTS: The study included 145,869 children. Maternal influenza vaccination during pregnancy was not associated with risk of small or large for gestational age births, preterm birth, need for mechanical ventilation at birth, respiratory distress syndrome, admission to the NICU, low birth weight, or low Apgar score. However, when we did not control for immortal time bias, the risk of preterm birth (odds ratio [OR]=0.69, 95% confidence interval [CI] 0.66-0.72) was lower among infants of vaccinated mothers. CONCLUSION: We found no association between maternal influenza vaccination during pregnancy and adverse birth outcomes. When investigating preterm birth outcome in association with vaccination during pregnancy, immortal time bias should be taken into account in the analysis.

Kaiser Permanente Northern California pregnancy database: Description and proof of concept study.

BACKGROUND/OBJECTIVE: We describe the establishment of a dynamic database linking mothers to newborns with the goal of studying vaccine safety in both pregnant women and their children and provide results of a study utilizing this database as a proof of concept. METHODS: All Kaiser Permanente Northern California (KPNC) live births and their mothers were eligible for inclusion in the pregnancy database. We used the medical record number (MRN), a unique identifier, to retrieve information about events that occurred during the pregnancy and at delivery and linked this same MRN to newborns for post-partum follow up. We conducted a retrospective cohort study to evaluate the association between receipt of tetanus, diphtheria and acellular pertussis (Tdap) vaccine during pregnancy and fever 0-3days after the first dose of diphtheria tetanus and acellular pertussis (DTaP) vaccine in the infant. The study included infants who were born at ⩾37weeks gestation from January 1, 2009 - October 1, 2015 and who received their first DTaP vaccine between 6 and 10weeks of age. We utilized diagnostic codes from inpatient, emergency department, outpatient clinics, and telephone calls. We identified fever using ICD 9 code 780.6, recorded temperature ⩾101 degree Fahrenheit, or parental report. RESULTS: The database contained the starting and ending date of each pregnancy and basic demographic characteristics of mothers and infants. There were 859,699 women and 873,753 children in the database as of January 2016. The proof of concept study included 148,699 infants. In a multivariable logistic regression analysis, Tdap vaccination during pregnancy was not associated with infant fever 0-3daysafter first dose of DTaP (adjusted odds ratio=0.92, 95% CI 0.82-1.04). CONCLUSION: The KPNC pregnancy database can be used for studies investigating exposure during pregnancy and outcomes in mothers and/or infants, particularly monitoring vaccine safety and effectiveness.

Demographic characteristics of members of the Vaccine Safety Datalink (VSD): A comparison with the United States population.

BACKGROUND: The Vaccine Safety Datalink (VSD) is a collaboration between CDC and nine integrated health care systems that serves as a cornerstone of US post-licensure vaccine safety monitoring. Given concerns that potential differences between the insured VSD population and the US population could limit the generalizability of VSD study findings, we performed a comparison of the demographic characteristics between the two populations. METHODS: We collected data from medical records and administrative files at VSD sites in 2010 to compare sex, age, race, ethnicity, income, and educational attainment to the 2010 US Census population. We also compared data on the 2012 VSD Medicaid population to 2012 US Medicaid data. RESULTS: The VSD population included over eight million individuals in 2010, which represented 2.6% of the total US population. All major demographic groups were represented in the VSD. We found no major differences in comparing sex, race, ethnicity, and educational attainment between the VSD and the US population. Middle income populations were comparable between the VSD and the US. While the percentage of lower income populations was less in the VSD compared to the US, the VSD had over two million individuals in this group. Additionally, there were over 600,000 Medicaid members in the VSD in 2012, which represented 1.1% of the US Medicaid population. CONCLUSIONS: We found that the VSD population is representative of the general US population on several key demographic and socioeconomic variables. Despite a few specific groups being underrepresented in the VSD compared to the US, the absolute number of VSD members is large enough to ensure significant representation of these groups in vaccine safety studies that use VSD data.