Phase II Study of Responses to Vaccination in Pediatric Cancer Survivors Following Standard-of-Care Non-HSCT...

Survivors of childhood cancer exhibit variable humoral immunity to vaccine-preventable diseases (VPDs) following cancer treatment. An increasing number of children are surviving a cancer diagnosis, making it imperative to document the extent to which survivors are at risk for VPDs and their response to vaccinations.

This Phase II prospective study included 65 pediatric patients diagnosed with cancer and treated with intensive chemotherapy without transplantation. Serum vaccine antibody concentrations were determined for 12 VPDs: tetanus, diphtheria, pertussis, polio, Haemophilus influenzae, pneumococcus, hepatitis B, meningococcus A, measles, mumps, rubella, and varicella following completion of cancer treatment and after vaccination.

Many patients lacked protective antibody levels to VPDs at the end of treatment. After vaccination, 87%-100% of patients had protective antibody titers against inactivated vaccines. The percentage of patients protected against the live attenuated vaccines was lower: measles (79%), mumps (83%), rubella (85%), and varicella (82%). Differences in response rates to vaccinations were not statistically significant for age (<7 vs. ≥7 years of age), diagnosis (hematologic disease vs. solid tumor), the time between the end of treatment and vaccination (3-6 vs. >6 months for inactivated vaccines), or between absolute lymphocyte count or CD4⁺ T-cell count at baseline.

For pediatric cancer survivors, a single dose of inactivated vaccines given 3 months following the end of treatment protects against these VPDs without the need for assessment of serostatus after inoculation. For live attenuated vaccines, patients require two inoculations for protection, and we recommend an assessment of serostatus to inform patients and providers of their risk for acquiring one of these communicable VPDs.