BACKGROUND AND PURPOSE:

• Duque et al. (Influenza, 2022) aimed to substantiate the value of the flu vaccine in pregnant individuals by measuring the effects of vaccination on pregnancy outcomes

METHODS:

• Retrospective cohort study
• Population
  • New Zealand residents
  • Pregnancy between 2003 and 2018
• Exposures
  • Influenza-associated maternal acute respiratory infection (ARI)
  • Flu vaccination
• Study design
  • Cox proportional hazards models were used to calculate crude and adjusted hazard ratios (aHRs)
• Primary outcomes
  • Pregnancy outcomes (e.g., fetal death and preterm birth)
  • Birth outcomes (e.g., low birthweight)

RESULTS:

• 822,391 pregnancies
  • ≥1 associated ARI hospitalization during the flu season: 0.6%
• Pregnancies with an ARI hospitalization were at an increased risk for
  • Preterm birth
    • aHR 1.50 (95% CI, 1.39 to 1.61)
  • Low birth weight
    • aHR 1.64 (95% CI, 1.51 to 1.79)
• There was no association between ARI hospitalization and fetal death
  • aHR 0.96 (95% CI, 0.69 to 1.34)
• Maternal influenza vaccination was associated with reduced risk for
  • Preterm birth
    • aHR 0.79 (95% CI, 0.77 to 0.82)
  • Low birthweight
    • aHR 0.87 (95% CI, 0.83 to 0.90)
  • Fetal death
    • aHR 0.50 (95% CI, 0.44 to 0.57)

CONCLUSION:

• An acute respiratory infection hospitalization during the flu season was associated with an increased risk for preterm birth and low birthweight
• Pregnant individuals who received a flu vaccine had lower risks for preterm birth, low birthweight, and fetal death
• The authors state

The value of influenza vaccination, in this case, goes beyond preventing mostly self-limited ARIs and seems to extend to the prevention of expensive and potentially deadly birth outcomes during influenza epidemic periods 

Learn More – Primary Sources:

Multi-decade national cohort identifies adverse pregnancy and birth outcomes associated with acute respiratory illness hospitalisations during the influenza season

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