Inactivated influenza vaccine during pregnancy and risks for adverse obstetric events.
OBJECTIVE
To compare risks for adverse obstetric events between females who did and did not receive trivalent inactivated influenza vaccine during pregnancy.


METHODS
This retrospective, observational cohort study was conducted at seven Vaccine Safety Datalink sites. Pregnancies were identified from administrative and claims data using a validated algorithm. Females vaccinated while pregnant from 2002 to 2009 were matched one-to-two with replacement to unvaccinated pregnant females. Using a generalized estimating equation method with a Poisson distribution and log link, we evaluated the association of trivalent inactivated influenza vaccine with 13 outcomes. Given our large sample size and multiple comparisons (19 contrasts), a cutoff for significance of P<.005 was selected a priori.


RESULTS
Our cohort included 74,292 vaccinated females matched on age, site, and pregnancy start date with 144,597 unvaccinated females. We did not observe increased risks within 42 days of vaccination for hyperemesis, chronic hypertension, gestational hypertension, gestational diabetes, proteinuria, or urinary tract infection. Using a risk window from vaccination through pregnancy end, we did not observe increased risks after vaccination for proteinuria, urinary tract infection, gestational hypertension, preeclampsia or eclampsia, chorioamnionitis, puerperal infection, venous complications, pulmonary embolism, or peripartum cardiomyopathy. A reduced risk for gestational diabetes after vaccination was detected (adjusted hazard rate ratio 0.88, 95% confidence interval 0.83-0.93), likely as a result of healthy vaccine bias or earlier detection among vaccinees.


CONCLUSIONS
In this large cohort, influenza vaccination during pregnancy was not associated with increased risks for medically attended adverse obstetric events.


METHODS
II.
Health Partners Institute for Education and Research, Minneapolis, Minnesota 55425, USA. Elyse.O.Kharbanda@HealthPartners.com
Elyse Olshen
EO
Kharbanda
Gabriela
G
Vazquez-Benitez
Heather
H
Lipkind
Allison
A
Naleway
Grace
G
Lee
James D
JD
Nordin
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007252:Influenza Vaccines / Q000009:adverse effects*; D008875:Middle Aged; D007744:Obstetric Labor Complications / Q000209:etiology*; D011247:Pregnancy; D012189:Retrospective Studies; D015164:Vaccines, Inactivated / Q000009:adverse effects*; D055815:Young Adult
D007252:Influenza Vaccines; D015164:Vaccines, Inactivated