Maternal and Fetal Outcomes Following Influenza Vaccination in Pregnancy

Study Overview
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Brief Summary
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This is a nationwide cohort study to assess maternal and fetal outcomes following vaccination with a quadrivalent influenza vaccine (QIV) during pregnancy.

Detailed Description
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The Korean National Immunization Program (NIP) first introduced quadrivalent influenza immunization for all pregnant women in the 2020-2021 season. This nationwide cohort study is proposed to assess the risks of adverse maternal and fetal outcomes following vaccination with a quadrivalent influenza vaccine (QIV) during pregnancy. We will use the national health insurance database from the National Health Insurance Service (NHIS) linked with the national immunization program registry data from the Korea Centers for Diseases Control & Prevention (KCDC).

Official Title
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Maternal and Fetal Outcomes Following Influenza Vaccination in Pregnancy

Conditions
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Pregnancy Related, Influenza Virus Vaccine Adverse Reaction

Intervention / Treatment
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* Biological: influenza vaccine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Pregnant women between September 22, 2020, and April 30, 2021. Exclusion Criteria: Women aged <20 or >45 years Pregnancies with a chromosomal abnormality Pregnancies with exposure to a known teratogenic medication

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 44 Years

Sexes Eligible for Study
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Female

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 |
| --- | --- |
| Pregnant women vaccinated with a QIV<br>Women aged 20-44 years who had received a QIV during their pregnancy between September 22, 2020, and April 30, 2021, under the national immunization program in South Korea. | Biological: influenza vaccine<br>* quadrivalent influenza vaccination in the flu seasons<br>|
| Pregnant women unvaccinated with a QIV<br>Women aged 20-44 years who had not received a QIV during their pregnancy between September 22, 2020, and April 30, 2021, under the national immunization program in South Korea. | Biological: influenza vaccine<br>* quadrivalent influenza vaccination in the flu seasons<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Risk of adverse pregnancy outcomes | Spontaneous abortion, stillbirth, neonatal death, congenital anomaly, pre-term birth, fetal growth restriction, small for gestational age, and low birth weight, which are confirmed by diagnostic records in the NHIS database. | from delivery up to 1 year after birth | 
| Risk of vaccine-related adverse events | Vaccine-related adverse events confirmed by diagnostic records in the NHIS database. | from delivery up to 1 year after birth | 
| Risk of poor health outcomes in pregnant women | Hospital admission, emergency department visits, influenza infection, and hospitalization with influenza infection, which are confirmed by diagnosis and healthcare utilization records in the NHIS database. | from delivery up to 1 year after birth | 
| Risk of poor health outcomes in neonates | Respiratory distress, neonatal intensive care unit admission, and hospital visits with neonatal infection or fever, which are confirmed by diagnosis and healthcare utilization records in the NHIS database. | from delivery up to 1 year after birth | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Risk of pregnancy-related complications | Pre-eclampsia/eclampsia, gestational diabetes mellitus, antenatal bleeding, postpartum hemorrhage, and maternal death, which are confirmed by diagnostic records in the NHIS database. | from delivery up to 1 year after birth |