Improving Viral Management for Pediatric Transplant Recipients

Improving Viral Management for Pediatric Transplant Recipients: Renewing Hope Through Research with Dr. Karina Top

Project investigator, Dr. Karina Top

Pediatric transplant recipients do not currently receive certain vaccines post-transplant as experts have deemed the live vaccines (including chicken pox, measles, mumps and rubella) to be a potential risk of infection. This leaves those children completely vulnerable in case of an outbreak in the community. A change in vaccination knowledge and guidelines for pediatric transplant recipients would ensure these kids would be protected, as well as eliminating the anxiety and stress for children and families.

In 2018, the Addison Fund of the Transplant Research Foundation of BC joined forces with the Canadian Donation and Transplantation Research Program (CDTRP) to fund a Research Innovation Grant looking at this important issue, and hopefully help keep transplant kids safe and healthy. The project, Optimizing varicella immunization in children living with transplants to prevent disease and improve long-term health, seeks to better understand vaccine efficacy in pediatric transplant recipients while exploring the safety around live vaccination.

We recently caught up with project team member Dr. Katrina Top, an infectious disease physician, to help us understand why this research is so important to improving the health and outcomes of young patients.

Tell us about your interest and connection to transplant?
I am a pediatric infectious disease physician and vaccine researcher with an interest in improving vaccination for people who are immunocompromised, including children with transplants. I became interested in doing research with this group because of the emerging data on the safety of live chickenpox vaccine in children with transplants who were unable to receive chickenpox vaccine before transplant.

You received funding through the Addison Fund of TRFBC for your project that re-examines varicella immunization in pediatric transplant recipients. Tells us more about this research and what it entails.
Based on studies showing that chickenpox vaccine is safe and effective in certain children with organ transplants, vaccine and transplant experts developed a guideline for determining which children with organ transplants could safely get the varicella vaccine. We are studying how to use this guideline in transplant clinics, to identify concerns that parents and healthcare providers have about chickenpox vaccination in children with liver, kidney and heart transplants, and confirm that the vaccine is safe and effective when given according to standard protocols based on the guideline. We are conducting interviews with healthcare providers and parents as well as following up children who receive chickenpox vaccine according to this new guideline.

Current guidelines advise transplant recipients, including children, to avoid attenuated (live) vaccines. How will your research expand these recommendations and what are the implications for recipients?
We have avoided giving chickenpox vaccine in children with transplants because it contains a weakened live virus due to concerns that it could cause chickenpox in children who are immunosuppressed. However, research has shown that children on low doses of immunosuppressive drugs to prevent rejection can safely receive the vaccine and be protected from chickenpox. We are evaluating the implementation of a recent international guideline developed by vaccine and transplant experts for determining which children with organ transplants could safely get the varicella vaccine. We will learn more about healthcare providers’ and parents’ concerns about live vaccines after transplant that will help us to introduce varicella vaccination in a way that addresses those concerns and ensures children get the vaccines they need. We will also confirm that our approach to chickenpox vaccination is safe and effective in children with organ transplants. In particular, we will learn more about how children with heart transplants respond to chickenpox vaccine; this group has not been included in most prior studies. By becoming immune to chickenpox through vaccination, more children with transplants will be able to avoid the discomfort, inconvenience and stress associated with potential exposures to chickenpox which in some cases requires giving preventive medications.

Why is this area of study so important to the overall health and wellbeing of pediatric transplant recipients?
In children with weakened immune systems due to medications given after organ transplant, varicella can cause pneumonia, encephalitis (brain infection), and even death. Although vaccination programs have made chickenpox uncommon, outbreaks still occur. Chickenpox can be very contagious and news of a child with chickenpox in school can raise alarm in transplant families and cause children with transplants to have to miss school to avoid getting exposed or even receive painful injections if they are in contact with someone with chickenpox. Being able to offer vaccination to these children would help to relieve much of that stress and inconvenience as well as risk of severe chickenpox to allow them to live fuller lives after transplant.

Do you anticipate this research leading to any new insights into the immune system of pediatric transplant recipients?
Yes, we will learn more about how well children with kidney, liver and heart transplants respond to chickenpox vaccine and their risk of adverse health events after vaccination. There is currently very little information about how safe and effective the vaccine is in children with heart transplants so we will learn more about this under-studied group.

How has COVID-19 impacted the progression of this important work?
Unfortunately, enrollment of children for vaccination has been on hold since March and some study sites also had to put a hold on recruiting parents and healthcare providers for interviews. We are now conducting interviews and are working on strategies to resume the vaccination portion of the study over the coming months.

On the topic of COVID-19, are there any trials or proposed vaccine projects currently being studied in immunocompromised patients?
At present, all the COVID-19 vaccine trials seem to involve only healthy adults. Hopefully, once vaccines have been confirmed to be safe and trigger an immune response in adults, trials will be done in immunocompromised adults so we will have some data to extrapolate to children. Vaccine trials in immunocompromised children are unlikely to happen until after a vaccine is approved for use in adults. There is a federal task force focused on COVID-19 in children that is working to identify and address knowledge gaps for the pediatric population, and immunocompromised children are likely to be a top priority.

Over 300 children in British Columbia are living with an organ transplant. These children are not little adults and have unique health needs and developmental concerns related to transplantation. Pediatric transplant research is vital to addressing these needs and concerns. To help make the future a little brighter for our youngest patients, please donate to the Addison Fund at