Maternal Influenza A(H1N1) Immunization During Pregnancy and Risk for Autism Spectrum Disorder in Offspring : A
Jonas F Ludvigsson1, Henric Winell2, Sven Sandin3
1Karolinska Institutet, Stockholm, and Örebro University Hospital, Örebro, Sweden, School of Medicine, University of Nottingham, Nottingham, United Kingdom, and Celiac Disease Center, Columbia University College of Physicians and Surgeons, New York, New York (J.F.L.).
Insights
Maternal influenza A(H1N1)pdm09 vaccination during pregnancy was not linked to an increased risk of autism spectrum disorder (ASD) in offspring. This large study found no association between the swine flu vaccine and ASD development.
Area of Science:
- Epidemiology
- Vaccinology
- Developmental Pediatrics
Background:
- Concerns exist regarding potential links between prenatal influenza vaccine exposure and autism spectrum disorder (ASD).
- The 2009 H1N1 influenza pandemic prompted widespread vaccination efforts, including during pregnancy.
Purpose of the Study:
- To investigate the association between maternal vaccination against influenza A(H1N1)pdm09 (swine flu) during pregnancy and the risk of ASD in offspring.
- To determine if first-trimester H1N1 vaccination influences ASD risk.
Main Methods:
- A population-based cohort study utilizing nationwide Swedish registers.
- Inclusion of live births between October 2009 and September 2010, with follow-up through December 2016.
- Cox regression analysis was employed to estimate hazard ratios for ASD and autistic disorder (AD), adjusting for potential confounders.
Main Results:
- Prenatal exposure to the H1N1 vaccine was not associated with an increased risk of ASD (adjusted hazard ratio [aHR], 0.95; 95% CI, 0.81 to 1.12) or autistic disorder (AD) (aHR, 0.96; CI, 0.80 to 1.16).
- Analysis restricted to first-trimester vaccination also showed no increased risk for ASD or AD.
- The 6-year cumulative incidence difference for ASD was 0.04% and for AD was 0.02% between exposed and unexposed children.
Conclusions:
- This large-scale cohort study provides evidence that maternal H1N1 vaccination during pregnancy is not associated with an elevated risk of autism spectrum disorder in offspring.
- The findings contribute to the understanding of vaccine safety during pregnancy.
Background:
There are concerns that influenza vaccine exposure during pregnancy may be associated with increased risk for autism spectrum disorder (ASD).
Objective:
To examine the risk for ASD in offspring of mothers who were vaccinated against influenza A(H1N1)pdm09 ("swine flu") during pregnancy.
Design:
Population-based cohort study using nationwide registers.
Setting:
Seven health care regions in Sweden.
Participants:
Live births between October 2009 and September 2010, with follow-up through December 2016. In total, 39 726 infants were prenatally exposed to H1N1 vaccine (13 845 during the first trimester) and 29 293 infants were unexposed.
Measurements:
Cox regression was used to estimate hazard ratios (HRs) for the primary outcome, ASD, before and after adjustment for potential confounders. The secondary outcome was autistic disorder (AD).
Results:
Mean follow-up was 6.7 years in both unexposed and exposed children. During follow-up, 394 (1.0%) vaccine-exposed and 330 (1.1%) unexposed children had a diagnosis of ASD. In adjusted analyses, prenatal exposure to H1N1 vaccination was not associated with a later diagnosis of ASD (adjusted HR [aHR], 0.95 [95% CI, 0.81 to 1.12]) or AD (aHR, 0.96 [CI, 0.80 to 1.16]). The 6-year standardized cumulative incidence difference between the unexposed and exposed children was 0.04% (CI, -0.09% to 0.17%) for ASD and 0.02% (CI, -0.09% to 0.14%) for AD. Restricting the analysis to vaccination in the first trimester of pregnancy did not influence risk estimates (aHR, 0.92 [CI, 0.74 to 1.16] for ASD and 0.91 [CI, 0.70 to 1.18] for AD).
Limitation:
Data on H1N1 influenza infection are lacking.
Conclusion:
This large cohort study found no association between maternal H1N1 vaccination during pregnancy and risk for ASD in the offspring.
Primary Funding Source:
Swedish Research Council.
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