Norwegian study suggests rise in childhood type 1 diabetes not caused by rotavirus vaccine

A comprehensive Norwegian study indicates an uptick in type 1 diabetes among children under five following rotavirus vaccine rollout, but researchers caution the vaccine is unlikely to be the cause amid broader environmental factors at play.

A large Norwegian study has found that the rate of type 1 diabetes in children under five rose after the country introduced its rotavirus vaccine in 2014, but the researchers say the vaccine is unlikely to be the reason.

The findings, presented at the annual meeting of the European Association for the Study of Diabetes in Milan and published in Diabetologia, come from a nationwide analysis of 740,744 children born in Norway between 2007 and 2019. By following children from six months to age five, the researchers recorded 846 cases of type 1 diabetes and identified an 11% relative increase in incidence after the vaccine rollout. The work was led by Maria Östman of the University of Oslo.

Rotavirus is a common cause of severe gastroenteritis in young children, and vaccination has sharply reduced hospital admissions and deaths linked to the infection. In Norway, the monovalent Rotarix vaccine is part of the national childhood immunisation programme, and uptake was high when it was introduced. The researchers used that rapid rollout as a natural experiment to test whether there was any association with type 1 diabetes, a condition that has long been suspected of being influenced by environmental triggers as well as genetics.

At first glance, the results appeared to show a higher incidence of type 1 diabetes after the vaccine was introduced. But the authors say several additional analyses point away from a causal link. They compared the rotavirus findings with changes in the Norwegian immunisation programme that were not expected to affect diabetes risk, including the introduction of hepatitis B vaccination and a switch in pneumococcal vaccine. Those comparisons showed a similar rise, suggesting the pattern may reflect broader changes over time rather than the vaccine itself.

The study’s secondary analysis also did not show a statistically significant increased risk among children who had received both doses of the vaccine compared with those who had not. On that basis, the researchers say they found no evidence that rotavirus vaccination lowers the risk of type 1 diabetes, but also no solid evidence that it raises it. Instead, they argue that the observed increase may be tied to other, still unidentified environmental factors. They noted that type 1 diabetes incidence has been rising overall in recent decades, with some year-to-year fluctuation, and pointed to the need for further studies in different settings and with different vaccines before drawing firm conclusions.

The authors also considered other possible explanations, including the effect of the Covid-19 pandemic on diabetes trends and changes to prenatal follow-up guidance in Norway, but they said neither fully accounted for the pattern in their data. Their overall message was cautious: the rise in incidence deserves attention, but the rotavirus vaccine itself is probably not the cause.