Researchers have found that H1N1 "swine flu" vaccination given to pregnant women might not be associated with an autism spectrum disorder in the offspring.

For our comprehensive coverage and latest updates on COVID-19 click here.

Autism spectrum disorder is a severe neurodevelopmental childhood disorder characterised by impaired communication, lack of social skills and repetitive behaviour. The disease has its onset in childhood. "Our null findings are important since some people have suspected that vaccinations could cause autism, and the anti-vaccine movement seems to be growing in the Western world," said study lead author Jonas F Ludvigsson from the Karolinska Institutet in Sweden.

While some studies indicate that influenza vaccination during pregnancy protects against morbidity in both the woman and her offspring, the long-term risks of H1N1 vaccination during fetal life have not been examined in detail. However, two recent studies were unable to rule out that offspring to women undergoing influenza or H1N1 influenza vaccination during pregnancy, and especially during the first trimester, were at increased risk of autism spectrum disorder. Now, a large study by researchers, published in the journal Annals of Internal Medicine, refutes any such association.Researchers, linked vaccination data in pregnant women from seven Swedish healthcare regions in 2009-2010 to the Swedish Medical Birth Register and the Swedish National Patient Register to identify autism spectrum disorder in the offspring.

Of the 39,726 vaccine-exposed children, 394 had a diagnosis of autism spectrum disorder during the six-year follow-up compared with 330 among 29,293 unexposed children. The researchers adjusted their analyses for such confounders as maternal smoking, height-weight, maternal age and comorbidity in order to minimize the influence of other factors that might explain any association between vaccination and autism.

Adjusting for potential confounders, H1N1 vaccine exposure during fetal life was not associated with a later childhood diagnosis of autism spectrum disorder. Results were similar for vaccinations in the first pregnancy trimester. "H1N1 vaccination has previously been linked to an increased risk of narcolepsy in young people, but vaccinating pregnant women does not seem to influence the risk of autism spectrum disorder in the offspring," Ludvigsson said. "Vaccination research has never been more important. Anticipating a vaccine against COVID-19, millions of pregnant women are likely to be offered such a vaccination," he added.