title: A/H1N1 pandemic influenza vaccination: A retrospective evaluation of adverse maternal, fetal and neonatal outcomes in a cohort of pregnant women in Italy.
abstract: Although concerns about safety of influenza vaccination during pregnancy have been raised in the past, vaccination of pregnant women was recommended in many countries during the 2009 A/H1N1 pandemic influenza. A retrospective cohort study was conducted to evaluate the risk of adverse maternal, fetal and neonatal outcomes among pregnant women vaccinated with a MF59-adjuvanted A/H1N1 pandemic influenza vaccine. The study was carried out in four Italian regions (Piemonte, Friuli-Venezia-Giulia, Lazio, and Puglia) among 102,077 pregnant women potentially exposed during the second or third trimester of gestation to the vaccination campaign implemented in 2009/2010. Based on data retrieved from the regional administrative databases, the statistical analysis was performed using the Cox proportional-hazards model, adjusting for the propensity score to account for the potential confounding effect due to the socio-demographic characteristics and the clinical and reproductive history of women. A total of 100,332 pregnant women were eligible for the analysis. Of these, 2003 (2.0%) received the A/H1N1 pandemic influenza vaccination during the second or third trimester of gestation. We did not observe any statistically significant association between the A/H1N1 pandemic influenza vaccination and different maternal outcomes (hospital admissions for influenza, pneumonia, hypertension, eclampsia, diabetes, thyroid disease, and anaemia), fetal outcomes (fetal death after the 22nd gestational week) and neonatal outcomes (pre-term birth, low birth weight, low 5-min Apgar score, and congenital malformations). Pre-existing health-risk conditions (hospital admissions and drug prescriptions for specific diseases before the onset of pregnancy) were observed more frequently among vaccinated women, thus suggesting that concomitant chronic conditions increased vaccination uptake. The results of this study add some evidence on the safety of A/H1N1 pandemic influenza vaccination during pregnancy but, because of the reduced statistical power, meta-analyses and large multi-centres studies are needed in order to obtain more conclusive results, especially for rare outcomes.
authors.affiliation: National Centre for Epidemiology, Surveillance and Health Promotion, Italian National Institute of Health, Viale Regina Elena 299, 00161 Rome, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Fabiani
authors.affiliation: National Centre for Epidemiology, Surveillance and Health Promotion, Italian National Institute of Health, Viale Regina Elena 299, 00161 Rome, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Bella
authors.affiliation: National Centre for Epidemiology, Surveillance and Health Promotion, Italian National Institute of Health, Viale Regina Elena 299, 00161 Rome, Italy.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Rota
authors.affiliation: Epidemiological Unit, Regional Central Directorate for Health, Social-Health Integration, Social Policy, and Family, Udine, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Clagnan
authors.affiliation: Department of Prevention, Local Health Unit 4 Medio Friuli, Udine, Italy.
authors.forename: Tolinda
authors.initials: T
authors.lastname: Gallo
authors.affiliation: Laziosanità-Agency for Public Health of Lazio Region, Rome, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: D'Amato
authors.affiliation: Laziosanità-Agency for Public Health of Lazio Region, Rome, Italy.
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pezzotti
authors.affiliation: SeREMI, Local Health Unit of Alessandria-Piemonte Region, Alessandria, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Ferrara
authors.affiliation: SeREMI, Local Health Unit of Alessandria-Piemonte Region, Alessandria, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Demicheli
authors.affiliation: Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Martinelli
authors.affiliation: Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy.
authors.forename: Rosa
authors.initials: R
authors.lastname: Prato
authors.affiliation: National Centre for Epidemiology, Surveillance and Health Promotion, Italian National Institute of Health, Viale Regina Elena 299, 00161 Rome, Italy. Electronic address: caterina.rizzo@iss.it.
authors.forename: Caterina
authors.initials: C
authors.lastname: Rizzo
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D064420:Drug-Related Side Effects and Adverse Reactions / Q000453:epidemiology* / Q000473:pathology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects*; D007251:Influenza, Human / Q000517:prevention & control*; D007558:Italy; D008875:Middle Aged; D011136:Polysorbates / Q000008:administration & dosage / Q000009:adverse effects; D011247:Pregnancy; D011256:Pregnancy Outcome; D037841:Pregnant People; D012189:Retrospective Studies; D013185:Squalene / Q000008:administration & dosage / Q000009:adverse effects; D014611:Vaccination / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines; C089950:MF59 oil emulsion; D011136:Polysorbates; D013185:Squalene
keywords: A/H1N1pdm09; Influenza; Pandemic vaccination; Pregnancy; Pregnancy outcomes; Safety