Vaccine-preventable infections such as influenza pose an ongoing threat to children undergoing allogeneic haematopoietic stem cell transplant (HSCT), a WA study has shown.

While revaccination programs  prevent most vaccine-preventable infections after HSCT, children with blood cancers are still at risk of influenza and herpes zoster, according to clinicians in the Department of Haematology and Oncology, Princess Margaret Hospital for Children, Perth.

In a retrospective review of infections among 71 children with cancers such as acute myeloid leukaemia (AML) and acute lymphoblastic leukaemia (ALL) receiving a first allogeneic HSCT in WA between 2005 and 2014, they found a low incidence for most infections covered by vaccines such as MMR, DTP and pneumococcal disease and pertussis vaccines.

However, one in five of the children (19.7%) developed a vaccine preventable disease, with the most common being influenza (7 children) and herpes zoster (six children).

The cases of influenza infection occurred an average of almost two years after HSCT, and despite four of the children having had trivalent flu vaccine. Four children were receiving ongoing immunosuppression at the time of infection, with chronic graft versus host disease being the indication for immunosuppression in three patients.  Influenza resulted in an average length of hospital stay of three days and none of the children infected required ICU treatment.

Varicella herpes zoster reactivation occurred in six children of whom four had stopped acyclovir prophylaxis while the remaining two patients had been non-compliant with their acyclovir prophylaxis.  Reactivation occurred a mean of 234 days after HSCT, with children developing shingles rash. The mean length of hospital stay was five days and one child died due to disseminated herpes zoster.

“All episodes occurred late, following day 100, and were therefore beyond the traditional ‘high-risk’ period for infectious morbidity; however, the risk in our patients was manifest by ongoing immune reconstitution and/or continued immunosuppressive therapy, the authors noted.

Lead author Dr Anne Ryan, a haematologist at Princess Margaret Hospital, said the overall survival in the children post HSCT was comparable to other Australian cohorts, with  five-year overall survival rates of  75% for matched sibling transplants and 63.3% for alternative donor transplants, respectively.

Nevertheless, the high rates of influenza and herpes zoster showed that more research was “desperately required” to inform the best ways to prevent these infections, she wrote.

For herpes zoster the focus would likely be on new recombination vaccines that are currently in development, she suggested.

The article is published in Journal of Paediatrics and Child Health.