In Wake of Measles Outbreaks, Another Study Dispels Myths Surrounding MMR Vaccine

With 206 cases of measles reported so far in 11 states in 2019, a new study noting that there is no connection between the measles, mumps, rubella (MMR) vaccine to autism has been released. The new study includes an analysis of subgroups of children that some of those opposed to vaccines have claimed (mainly without evidence) might be more vulnerable to perceived effects.

The study, published Monday in the Annals of Internal Medicine, is one of the largest studies to date about the issue. The researchers involved in this study indicated they were adding to their previous body of work specifically to address previous concerns.

Researchers used a nationwide cohort of children born between 1999 and 2010, drawn from the Danish Psychiatric Central Register from Denmark, where the childhood vaccination program is voluntary and free.

The cohort included 657,461 children contributing over 5 million person-years of follow-up between January 1, 2000, through August 31, 2013; during the follow-up, 6517 children were diagnosed with autism (incident rate 129.7 per 100,000 person-years).

Comparing MMR-vaccinated with MMR-unvaccinated children yielded a fully adjusted autism hazard ratio of 0.93 (95% CI, 0.85 to 1.02). More importantly, no increased risk for autism after MMR vaccination was seen in subgroups of children that are the focus of concern by some hesitant to trust vaccines: children with siblings affected by autism, autism risk factors (based on a disease risk score) or other childhood vaccinations, or during specified time periods after vaccination.

In addition, researchers included children with no vaccination in the first year of life for DTaP-IPV/HIB and found no evidence of a link between MMR and autism in that group. That inclusion was also made to address concerns about other studies.

The researchers said this work adds to previous studies through "significant additional statistical power and by addressing hypotheses of susceptible subgroups and clustering of cases.”

In an accompanying editorial, physicians at Emory University wrote that, "in an ideal world vaccine safety research would be conducted only to evaluate scientifically grounded hypotheses, not in response to the conspiracy du jour.” ² However, they acknowledged that continued questioning put forth by those skeptical of vaccine safety can affect public confidence and vaccine uptake. On the other hand, having scientists perform additional research simply to add to the already substantial pile of evidence about the MMR’s safety comes at an opportunity cost about other lines of research.

The World Health Organization recently called vaccine hesitancy 1 of the top 10 threats to global health in 2019. Severe cases of measles can be life-threatening; for every 1000 children infected with measles, 1 or 2 will die of it, according to the CDC. Serious complications can include encephalitis and pneumonia.

References

1. Hviid A, Hansen JV, Frisch M, Melbye M. Measles, mumps, rubella vaccination and autism: a nationwide cohort study. Ann Intern Med.
2. Omer SB, Yildirim I. Further evidence of MMR vaccine safety: scientific and communications considerations. Ann Intern Med.