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PLoS One. 2016 Aug 3;11(8):e0160342. doi: 10.1371/journal.pone.0160342. eCollection 2016.

Infant Respiratory Outcomes Associated with Prenatal Exposure to Maternal 2009 A/H1N1 Influenza Vaccination.

Fell DB1, Wilson K2,3,4, Ducharme R3,4, Hawken S3,4,5, Sprague AE1, Kwong JC3,6,7,8, Smith G9, Wen SW4,10, Walker MC1,4,10,11.

Author information

1
Better Outcomes Registry & Network (BORN) Ontario, Ottawa, Ontario, Canada.
2
Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
3
Institute for Clinical Evaluative Sciences, Ottawa and Toronto, Ontario, Canada.
4
Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
5
School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa, Ontario, Canada.
6
Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
7
Public Health Ontario, Toronto, Ontario, Canada.
8
Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada.
9
Department of Obstetrics & Gynaecology, Queen's University, Kingston, Ontario, Canada.
10
OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada.
11
Department of Obstetrics, Gynecology and Newborn Care, The Ottawa Hospital, Ottawa, Ontario, Canada.

Abstract

BACKGROUND:

Infants are at high risk for influenza illness, but are ineligible for vaccination before 6 months. Transfer of maternal antibodies to the fetus has been demonstrated for 2009 A/H1N1 pandemic vaccines; however, clinical effectiveness is unknown. Our objective was to evaluate the association between 2009 A/H1N1 pandemic vaccination during pregnancy and rates of infant influenza and pneumonia.

METHODS:

We linked a population-based birth cohort to administrative databases to measure rates of influenza and pneumonia diagnosed during ambulatory physician visits, hospitalizations and emergency department visits during one year of follow-up. We estimated incidence rate ratios and 95% confidence intervals (95% CI) using Poisson regression, comparing infants born to A/H1N1-vaccinated women (vaccine-exposed infants) with unexposed infants, adjusted for confounding using high-dimensional propensity scores.

RESULTS:

Among 117,335 infants in the study, 36,033 (31%) were born to A/H1N1-vaccinated women. Crude rates of influenza during the pandemic (per 100,000 infant-days) for vaccine-exposed and unexposed infants were similar (2.19, 95% CI: 1.27-3.76 and 3.60, 95% CI: 2.51-5.14, respectively), as were crude rates of influenza and pneumonia combined. We did not observe any significant differences in rates of study outcomes between study groups during the second wave of the 2009 A/H1N1 pandemic, nor during any post-pandemic time period.

CONCLUSION:

We observed no difference in rates of study outcomes among infants born to A/H1N1-vaccinated mothers relative to unexposed infants born during the second A/H1N1 pandemic wave; however, due to late availability of the pandemic vaccine, the available follow-up time during the pandemic time period was very limited.

PMID:
27486858
PMCID:
PMC4972313
DOI:
10.1371/journal.pone.0160342
[Indexed for MEDLINE]
Free PMC Article

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