Anti-influenza vaccination in pregnancy

What risks does influenza pose for a pregnant woman?

Pregnant women in the second and third trimester of gestation during seasonal flu period are one of the categories to which vaccination is actively and freely offered 1.

If the infection occurs at this stage, there is a greater risk of developing complications for the pregnant woman 2,3,4 and for her foetus. These include:

  • Hospitalisation of the mother2.3
  • Pre-term birth5
  • Foetal distress5
  • Caesarean section5
  • Reduction of foetal growth6
  • Hospitalisation of the newborn in the first 5 months of life7

Is the flu vaccine risky in pregnancy?

The scientific literature available highlights that:

  • Children of vaccinated mothers are more protected from influenza up to 6 months of life8
  • Vaccination of the mother is a protective factor for low birth weight and low weight for gestational age9
  • Maternal vaccination does not increase in any way the risk of foetal complications (foetal death, miscarraige10 and congenital malformations11)
  • There is a very slight increase in the risk of gestational diabetes and preeclampsia11

Are pregnant women informed on this subject?

An Australian study published in 2013 found that a quarter of the female population in pregnancy is completely unaware of the vaccination offer and 34% even believe that it is contraindicated12. Most women, however, have requested vaccination after receiving information from healthcare personnel11,13,14.

It is therefore of prime importance that health personnel are prepared to spread correct information on such a relevant public health topic.

Sources / Bibliography
  1. Ministero della Salute. Prevenzione e controllo dell’influenza: raccomandazioni per la stagione 2014-2015.
  2. “1 o 2 donne su 1000 vanno incontro ad ospedalizzazione” Mak TK, Mangtani P, Leese J, Watson JM, Pfeifer D. Influenza vaccination in pregnancy: current evidence and selected national policies.Lancet Infect Dis 2008; 8:44-5
  3. “il rischio di ricovero è 18 volte superiore rispetto alle donne sane non in gravidanza“ Schanzer DL, Langley JM, Tam TWS. Influenza-attributed hospitalization rates among pregnant women in Canada 1994-2000. J Obstet Gynecol Can 2007; 29:622-9. 2
  4. il rischio di decesso aumenta di 4 volte rispetto al resto della popolazione” Ashley J, Smith T, Dunnell K. Deaths in Great Britain associated with the influenza epidemic of 1989/90. Popul Trends 1991; 65: 16–20.
  5. Cox S, Posner SF, McPheeters M, Jamieson DJ, Kourtis AP,Meikle S. Hospitalizations with respiratory illness among pregnant women during infl uenza season. Obstet Gynecol 2006; 107: 1315–22.
  6. Pierce M, Kurinczuk JJ, Spark P, Brocklehurst P, KnightM; UKOSS. Perinatal outcomes after maternal 2009/H1N1 infection: national cohort study. BMJ. 2011 Jun14; 342:d3214.
  7. Poehling KA, Edwards KM, Weinberg GA, et al. The underrecognized burden of influenza in young children. N Engl J Med 2006; 355: 31–40.
  8. “le infezioni da virus influenzale sono ridotte del 63%, le patologie respiratorie febbrili del 29%” Zaman K, Roy E, Arifeen SE, et al. Effectiveness of maternal influenza immunization in mothers and infants. N Engl J Med 2008; 359:1555-64.
  9. Steinhoff MC, Omer SB, Roy E, El Arifeen S, Raqib R, Dodd C, Breiman RF, Zaman K. Neonatal outcomes after influenza immunization during pregnancy: a randomized controlled trial. CMAJ. 2012 Apr 3;184(6):645-53.
  10. Pasternak B, Svanström H, Mølgaard-NielsenD, Krause TG, Emborg HD, MelbyeM, HviidA. Vaccination against pandemicA/H1N1 2009 influenza in pregnancy and risk of fetal death: cohort study in Denmark. BMJ. 2012 May 2;344:e2794
  11. Trotta F, Da Cas R, Spila Alegiani S, Gramegna M, Venegoni M, Zocchetti C, Traversa Evaluation of safety of A/H1N1 pandemic vaccination during pregnancy: cohort studyBMJ. 2014 May 29; 348:g3361G.
  12. KE Wiley, PD Massey, SC Cooper et al, Uptake of influenza vaccine by pregnant women: a cross sectional survey Med J Aus 2013; 198:373-375
  13. Frew PM, Saint-Victor DS, Owens LE et al, Socioecological and message framing factors influencing maternal influenza immunization among minority women. Vaccine, 2014 Mar 26;32(15):1736-44.
  14. Maher L, Hope K, Torvaldsen S et al, ‘Influenza vaccination during pregnancy: coverage rates and influencing factors in two urban districts in Sydney’. Vaccine, 2013 Nov 12:31(47):5557-64.
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