Certain Live Vaccines Safe and Effective in Pediatric Organ Transplant Patients, Study Finds

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Live vaccinations may be safe and effective for protection against measles, mumps, and varicella in certain pediatric recipients who have had a solid organ transplant, according to an investigation published earlier this month in JAMA Network Open.

Historically, guidelines have recommended against using live vaccines in certain immunocompromised individuals, such as those receiving a solid organ transplant (SOT). While non-live alternatives exist for some vaccines, two important childhood vaccines, measles-mumps-rubella (MMR) and varicella-zoster virus (VZV), only come as live, attenuated vaccines. As such, most pediatric transplant patients have simply gone without these vaccines, leaving these children at higher risk.

Measles, mumps, and varicella outbreaks have increased over the last few decades in the US, with more than 1,200 measles cases reported in 2019, according to the Centers for Disease Control and Prevention.

To address this, researchers across the U.S. sought to understand the safety and efficacy of administering live vaccines to pediatric SOT patients. In an effort to answer these questions, investigators from 18 different children’s hospitals and health centers developed this study.

From 2003 through 2022, each of the 18 sites enrolled pediatric liver or kidney transplant recipients without a history of MMR or VZV vaccination. Each patient received between 1 and 3 doses of both MMR and VZV. The investigators focused on two main outcomes: safety and effectiveness. They collected safety data, including any immediate reactions to the vaccine as well as any occurrence of any potential vaccine-induced infection or transplant rejection. Additionally, the team analyzed vaccine effectiveness by assessing each patient’s ability to generate and retain immune response (antibodies) against the respective viruses.

Overall, 281 children participated in this trial. From a safety perspective, no short-term adverse events occurred. Similarly, only five participants developed varicella, which in each case resolved within one week; no cases of measles, rubella, or transplanted organ rejection were reported.

Live MMR and VZV vaccines appeared relatively effective, as well. A majority of trial participants exhibited antibodies against the various infections after vaccination. At the three-month follow-up, the following proportion of the participants displayed antibodies for the four target viruses: 107 out of 149 (72%) for varicella, 130 out of 152 (86%) for measles, 100 out of 120 (83%) for mumps, and 124 out of 125 (99%) for rubella. One year post-vaccination, most children maintained protective antibody levels.

First and corresponding author Amy G. Feldman, M.D., of the University of Colorado and Children’s Hospital Colorado and the other nvestigators acknowledged that the observational design of the study prevented a comparison between pretransplant antibody levels and post-transplant antibody levels. Still, the study findings reflect an important step towards increased access to disease protection.

Feldman and her colleagues wrote that more research is needed to understand how long protection lasts after live vaccine administration in children who have received organ transplants and to explore the factors that affect immune response and clinical protection in these recipients.