Abstract
Objectives
Influenza vaccination rate among pregnant women has typically been low, and there is little population-based information on predictors of vaccination uptake within this group. This study aimed to evaluate the rate of influenza vaccination in pregnant women during the 2009 H1N1 influenza pandemic and explore predictors associated with receiving vaccination during pregnancy.
Methods
We conducted a retrospective population-based cohort analysis involving women who gave birth in an Ontario hospital between November 2, 2009 and April 30, 2010. Rates of influenza vaccination were calculated according to maternal, obstetrical, behavioural and neighbourhood characteristics. Women who received influenza vaccination during pregnancy were compared with women who were not vaccinated using log-binomial regression to calculate adjusted relative risks (aRR) and 95% confidence intervals (CI).
Results
Among 56,654 women who gave birth in the study period, 42.6% had received influenza vaccination during pregnancy. Vaccine uptake was lower among women: of age <20 (aRR=0.80, 95% CI: 0.76–0.84), in lower socio-economic status (aRR=0.93, 95% CI: 0.90–0.96), without an antenatal care provider (aRR=0.72, 95% CI: 0.59–0.88), who did not initiate antenatal care in a timely manner (aRR=0.93, 95% CI: 0.91–0.96), who smoked during pregnancy (aRR=0.92, 95% CI: 0.89–0.95), and with a history of preterm birth (aRR=0.97, 95% CI:0.94-1.00). An increased vaccination rate was observed among women with medical co-morbidities (aRR=1.10, 95% CI: 1.07–1.13) and with family physicians (vs. obstetricians) as antenatal care providers (aRR=1.08, 95% CI: 1.06–1.10).
Conclusion
We identified the prenatal population that may benefit from targeted public health intervention strategies to improve future vaccination rates for this priority vaccination group.
Key words: Influenza vaccination, pregnant women, H1N1
Résumé
Objectifs
Les taux de vaccination contre la grippe sont généralement faibles chez les femmes enceintes, et il existe peu de données populationnelles sur les prédicteurs du recours à la vaccination dans ce groupe. Nous avons voulu évaluer le taux de vaccination antigrippale chez les femmes enceintes durant la pandémie de grippe H1N1 de 2009 et explorer les prédicteurs associés à la vaccination durant la grossesse.
Méthode
Nous avons mené une étude de cohorte rétrospective dans la population des femmes ayant accouché dans un hôpital de l’Ontario entre le 2 novembre 2009 et le 30 avril 2010. Les taux de vaccination contre la grippe ont été calculés selon des caractéristiques maternelles, obstétriques, comportementales et du quartier. Nous avons comparé les femmes ayant reçu le vaccin contre la grippe durant leur grossesse aux femmes n’ayant pas été vaccinées, en calculant les risques relatifs ajustés (RRa) et les intervalles de confiance (IC) de 95 % par régression log-binomiale.
Résultats
Sur les 56 654 femmes ayant accouché durant la période de l’étude, 42,6 % ont reçu le vaccin contre la grippe durant leur grossesse. Le recours au vaccin était plus faible chez les femmes de <20 ans (RRa=0,80, IC de 95 %: 0,76–0,84), de faible statut socioéconomique (RRa=0,93, IC de 95 %: 0,90–0,96), sans fournisseur de soins prénatals (RRa=0,72, IC de 95 %: 0,59–0,88), n’ayant pas amorcé les soins prénatals à temps (RRa=0,93, IC de 95 %: 0,91–0,96), ayant fumé pendant leur grossesse (RRa=0,92, IC de 95 %: 0,89–0,95) et ayant des antécédents d’accouchement avant terme (RRa=0,97, IC de 95 %: 0,94–1,00). Un taux de vaccination accru a été observé chez les femmes ayant des comorbidités médicales (RRa=1,10, IC de 95 %: 1,07–1,13) et chez celles ayant un médecin de famille (plutôt qu’un obstétricien) comme fournisseur de soins prénatals (RRa=1,08, IC de 95 %: 1,06–1,10).
Conclusion
Nous avons cerné la population prénatale qui pourrait bénéficier de stratégies d’intervention de santé publique ciblées afin d’améliorer les taux de vaccination futurs dans ce groupe prioritaire sur le plan vaccinal.
Mots clés: vaccins antigrippaux, femmes enceintes, H1N1
Footnotes
Acknowledgements: Dr. Mark Walker is supported by a University of Ottawa tier 1 chair in Perinatal Epidemiology. The authors thank the health care providers and hospital staff throughout Ontario hospitals who collected these data. We also acknowledge Barbara Chapman, Monica Prince and the Better Outcomes Registry & Network (BORN) Ontario Regional Coordinators (Tammy Budhwa, Laurie Doxtator, Sandra Dunn, Glenda Hicks, Vivian Holmberg, Susan Jewell, Pam Robertson) for their dedication to ensuring that the data collection was a success. Financial assistance for the H1N1 data collection in the BORN Ontario database was provided by the Public Health Agency of Canada as part of the public health response to the H1N1 influenza pandemic. This study was funded by the Canadian Institutes of Health Research (Grant # 218563).
Conflict of Interest: None to declare.
References
- 1.Jamieson DJ, Theiler RN, Rasmussen SA. Emerging infections and pregnancy. Emerg Infect Dis. 2006;12(11):1638–43. doi: 10.3201/eid1211.060152. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Siston AM, Rasmussen SA, Honein MA, Fry AM, Seib K, Callaghan WM, et al. Pandemic 2009 influenza A(H1N1) virus illness among pregnant women in the United States. JAMA. 2010;303(15):1517–25. doi: 10.1001/jama.2010.479. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Dodds L, McNeil SA, Fell DB, Allen VM, Coombs A, Scott J, et al. Impact of influenza exposure on rates of hospital admissions and physician visits because of respiratory illness among pregnant women. CMAJ. 2007;176(4):463–68. doi: 10.1503/cmaj.061435. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Freeman DW, Barno A. Deaths from Asian influenza associated with pregnancy. Am J Obstet Gynecol. 1959;78:1172–75. doi: 10.1016/0002-9378(59)90570-8. [DOI] [PubMed] [Google Scholar]
- 5.Statement on influenza vaccination for the 2007–2008 season. An Advisory Committee Statement (ACS) Can Commun Dis Rep. 2007;33(ACS-7):1–38. [PubMed] [Google Scholar]
- 6.Harper SA, Fukuda K, Uyeki TM, Cox NJ, Bridges CB. Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP) MMWR Recomm Rep. 2004;53(RR-6):1–40. [PubMed] [Google Scholar]
- 7.Englund JA, Mbawuike IN, Hammill H, Holleman MC, Baxter BD, Glezen WP. Maternal immunization with influenza or tetanus toxoid vaccine for passive antibody protection in young infants. J Infect Dis. 1993;168(3):647–56. doi: 10.1093/infdis/168.3.647. [DOI] [PubMed] [Google Scholar]
- 8.Munoz FM, Greisinger AJ, Wehmanen OA, Mouzoon ME, Hoyle JC, Smith FA, et al. Safety of influenza vaccination during pregnancy. Am J Obstet Gynecol. 2005;192(4):1098–106. doi: 10.1016/j.ajog.2004.12.019. [DOI] [PubMed] [Google Scholar]
- 9.Fell DB, Sprague AE, Liu N, Yasseen AS, 3rd, Wen SW, Smith G, et al. H1N1 influenza vaccination during pregnancy and fetal and neonatal outcomes. Am J Public Health. 2012;102(6):e33–e40. doi: 10.2105/AJPH.2011.300606. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Zaman K, Roy E, Arifeen SE, Rahman M, Raqib R, Wilson E, et al. Effectiveness of maternal influenza immunization in mothers and infants. N Engl J Med. 2008;359(15):1555–64. doi: 10.1056/NEJMoa0708630. [DOI] [PubMed] [Google Scholar]
- 11.Naleway AL, Smith WJ, Mullooly JP. Delivering influenza vaccine to pregnant women. Epidemiol Rev. 2006;28:47–53. doi: 10.1093/epirev/mxj002. [DOI] [PubMed] [Google Scholar]
- 12.Fiore AE, Shay DK, Broder K, Iskander JK, Uyeki TM, Mootrey G, et al. Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. MMWR Recomm Rep. 2009;58(RR-8):1–52. [PubMed] [Google Scholar]
- 13.Strategic Advisory Group of Experts on Immunization - Report of the extraordinary meeting on the influenza A H1N1 2009 pandemic, 7 July 2009. Wkly Epidemiol Rec. 2009;84(30):301–4. [PubMed] [Google Scholar]
- 14.Public Health Agency of Canada. Guidance document on the use of pandemic influenza A (H1N1) 2009 Inactivated Monovalent Vaccine. 2009. [Google Scholar]
- 15.Seasonal influenza2009 H1N1 influenza vaccination coverage among pregnant women—10 states, 2009–10 influenza season. MMWR Morb Mortal Wkly Rep. 2010;59(47):1541–45. [PubMed] [Google Scholar]
- 16.Freund R, Le RC, Charlier C, Avenell C, Truster V, Treluyer JM, et al. Determinants of non-vaccination against pandemic 2009 H1N1 influenza in pregnant women: A prospective cohort study. PLoS One. 2011;6(6):e20900. doi: 10.1371/journal.pone.0020900. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Gilmour H, Hofmann N. H1N1 vaccination. Health Rep. 2010;21(4):63–69. [PubMed] [Google Scholar]
- 18.Gracie S, Metcalfe A, Dolan SM, Kehler H, Siever J, Tough S. Utilization of the 2009 H1N1 vaccine by pregnant women in a pandemic year. J Obstet Gynaecol Can. 2011;33(2):127–33. doi: 10.1016/S1701-2163(16)34797-1. [DOI] [PubMed] [Google Scholar]
- 19.White SW, Petersen RW, Quinlivan JA. Pandemic (H1N1) 2009 influenza vaccine uptake in pregnant women entering the 2010 influenza season in Western Australia. Med J Aust. 2010;193(7):405–7. doi: 10.5694/j.1326-5377.2010.tb03970.x. [DOI] [PubMed] [Google Scholar]
- 20.Broughton DE, Beigi RH, Switzer GE, Raker CA, Anderson BL. Obstetric health care workers’ attitudes and beliefs regarding influenza vaccination in pregnancy. Obstet Gynecol. 2009;114(5):981–87. doi: 10.1097/AOG.0b013e3181bd89c2. [DOI] [PubMed] [Google Scholar]
- 21.Ding H, Santibanez TA, Jamieson DJ, Weinbaum CM, Euler GL, Grohskopf LA, et al. Influenza vaccination coverage among pregnant women—National 2009 H1N1 Flu Survey (NHFS) Am J Obstet Gynecol. 2011;204(6Suppl1):S96–S106. doi: 10.1016/j.ajog.2011.03.003. [DOI] [PubMed] [Google Scholar]
- 22.Fabry P, Gagneur A, Pasquier JC. Determinants of A (H1N1) vaccination: Cross-sectional study in a population of pregnant women in Quebec. Vaccine. 2011;29(9):1824–29. doi: 10.1016/j.vaccine.2010.12.109. [DOI] [PubMed] [Google Scholar]
- 23.Fisher BM, Scott J, Hart J, Winn VD, Gibbs RS, Lynch AM. Behaviors and perceptions regarding seasonal and H1N1 influenza vaccination during pregnancy. Am J Obstet Gynecol. 2011;204(6Suppl1):S107–S111. doi: 10.1016/j.ajog.2011.02.041. [DOI] [PubMed] [Google Scholar]
- 24.Fridman D, Steinberg E, Azhar E, Weedon J, Wilson TE, Minkoff H. Predictors of H1N1 vaccination in pregnancy. Am J Obstet Gynecol. 2011;204(6Suppl1):S124–S127. doi: 10.1016/j.ajog.2011.04.011. [DOI] [PubMed] [Google Scholar]
- 25.Ozer A, Arikan DC, Kirecci E, Ekerbicer HC. Status of pandemic influenza vaccination and factors affecting it in pregnant women in Kahramanmaras, an eastern Mediterranean city of Turkey. PLoS One. 2010;5(12):e14177. doi: 10.1371/journal.pone.0014177. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Steelfisher GK, Blendon RJ, Bekheit MM, Mitchell EW, Williams J, Lubell K, et al. Novel pandemic A (H1N1) influenza vaccination among pregnant women: Motivators and barriers. Am J Obstet Gynecol. 2011;204(6Suppl1):S116–S123. doi: 10.1016/j.ajog.2011.02.036. [DOI] [PubMed] [Google Scholar]
- 27.Tong A, Biringer A, Ofner-Agostini M, Upshur R, McGeer A. A cross-sectional study of maternity care providers’ and women’s knowledge, attitudes, and behaviours towards influenza vaccination during pregnancy. J Obstet Gynaecol Can. 2008;30(5):404–10. doi: 10.1016/S1701-2163(16)32825-0. [DOI] [PubMed] [Google Scholar]
- 28.McNutt L-A, Wu C, Xue X, Hafner JP. Estimating the relative risk in cohort studies and clinical trials of common outcomes. Am J Epidemiol. 2003;157(10):940–43. doi: 10.1093/aje/kwg074. [DOI] [PubMed] [Google Scholar]
- 29.Yeager DP, Toy EC, Baker B., III Influenza vaccination in pregnancy. Am J Perinatol. 1999;16(6):283–86. doi: 10.1055/s-2007-993873. [DOI] [PubMed] [Google Scholar]
- 30.Society of ObstetriciansGynaecologists of Canada. Experts recommend that all pregnant women over 20 weeks gestation get H1N1 vaccination immediately. 2009. [Google Scholar]