Revaccination of children with acute lymphoblastic leukemia following completion of chemotherapy

Intensive chemotherapy for acute lymphoblastic leukemia (ALL) may affect the immune system and potentially the immune memory causing antibodies provided by vaccination to disappear. There are disagreements regarding the guidelines for posttreatment immunization strategy.

Ninety-six children (aged 1-18 years at diagnosis) who completed chemotherapy for ALL were recruited. Antibody levels in the patient's serum against measles, varicella, polio, pertussis, hepatitis A, and hepatitis B were tested after completion of chemotherapy in patients who were fully vaccinated against these agents. Children who did not have positive serology to specific agents were revaccinated with a single dose accordingly. Antibody concentrations were measured again at least 4 weeks after revaccination.

Positive antibody levels varied between the different agents. The highest percentage of positive serology was against polio (87%) and the lowest against pertussis (4%) (p < .001). There were significant differences between patients with high risk (HR) and non-HR ALL regarding serology status for some vaccines. After revaccination, the levels of response to each booster dose were significantly different: 100% after booster dose for varicella and polio, and only 34% after pertussis booster.

Loss of humoral protection for vaccine preventable diseases is a common finding among patients with ALL. Revaccination with one dose of vaccine after completion of chemotherapy achieved seroconversion in 34-100% of the patients depending on the type of vaccine. We recommend this revaccination schedule to all children who completed ALL therapy and were previously fully vaccinated.