Children with rheumatic diseases such as juvenile arthritis often take medicines that dampen the immune system. That raises a practical question for families and doctors: are vaccines safe for these children, and do they protect as well as they should? Doctoral research at UMC Utrecht, the university hospital in the Utrecht Science Park, offers some answers.

According to a UMC Utrecht news item published on 12 October 2026, physician-researcher Mohamad Hamad Saied of the Kinderreumacentrum at the Wilhelmina Children's Hospital defended his PhD at Utrecht University in October 2026. His supervisors, as named by the hospital, are Joris van Montfrans and Bas Vastert, with Marc Jansen and Joost Swart as co-supervisors, all at the same centre. The hospital's account describes three published studies.

A measles, mumps and rubella booster

In the first study, researchers retrospectively followed 186 children with juvenile arthritis who received a booster against measles, mumps and rubella. Just over half were taking classic rheumatology medicines and just over a quarter were taking biologicals, a class of targeted drugs. Disease activity did not significantly increase after vaccination. Seven percent of the children had mild side effects, and no serious side effects were reported.

How long protection lasts

A follow-up of 182 children looked at protection over time. Five years after the booster, 60 percent of the children who had been on biologicals when vaccinated still had measles antibodies above the protective threshold. Among children who had not taken biologicals, the figure was 86 percent.

COVID-19 vaccination

The third study was a prospective cohort study covering 157 children with rheumatic inflammatory diseases. Those on biologicals had fewer antibodies, but according to UMC Utrecht they did not have more symptomatic COVID-19 infections than vaccinated children not on these medicines. Of the children studied, 91 percent showed a measurable, adequate T-cell response, a second arm of the immune defence. No serious vaccine-related side effects were reported.

What the research recommends

The hospital summarises the practical advice as follows: check a child's vaccination status at diagnosis and whenever treatment changes. For children who had biologicals at the time of the measles booster, consider a targeted antibody check around five years later, after which a specialist can judge whether an extra dose is appropriate. In complex cases, rheumatologists should decide together with immunology and infectious-disease specialists.

The hospital also stresses a caveat: low antibody levels do not automatically mean a child is unprotected, because the immune system retains a memory that can still recognise and fight a pathogen.

What the findings mean

The results are reassuring, but they do not establish one vaccination schedule for every child with rheumatic disease. Treatment, disease activity and vaccination history differ between patients, and the researchers' practical recommendation is for targeted assessment rather than automatic extra doses. Parents should discuss vaccination with their child's treating doctor; this article is not medical advice.

For Utrecht, the work is a reminder that the university hospital's children's centre produces research with direct use in clinics elsewhere: simple, checkable steps for a group of young patients whose immune protection is harder to take for granted.