Response of live vaccines administered to clinically immunocompetent patients with a 22q11.2 chromosomal microdeletion

Immunization with live viral vaccines for children with microdeletion 22q11.2 has been controversial due to concern over whether these patients have normal immune function and successfully develop protective antibody levels. We suspect that a history of clinical immunocompetence predicts safe and successful vaccination in these patients. Clinical immunocompetence and prior infections and vaccinations with measles, mumps, rubella (MMR) and varicella were retrieved from charts, data bases, and telephone interviews. Assessment of the immune system (T cell panel, quantitative immunoglobulins, mitogen stimulation to phytohemagglutinin (PHA), pokweed mitogen (PWM), and concanavalin (Con A), and antibody titers to MMR and varicella) was obtained. Patients without protective antibody levels and those without a history of prior vaccinations that were immunocompetent by clinical and chart review were vaccinated and evaluated for seroconversion 6 weeks post-vaccination. Eleven patients with 22q11.2 chromosomal microdeletion were reviewed: 1 had normal laboratory evaluation, 1 had low lymphocyte numbers, 1 had low QIGs, 1 had low lymphocyte numbers and low PWM mitogen response, 3 had low titers to MMR and varicella with subsequent seroconversion, 1 had low titer to MMR with subsequent seroconversion, 2 had low titers to varicella with subsequent seroconversion, 1 had low lymphocyte numbers and low titer to varicella with subsequent seroconversion. All patients with 22q11.2 chromosomal microdeletion who demonstrated clinical immunocompetence mounted protective antibody responses to MMR and varicella. Patients with 22q11.2 chromosomal microdeletion and a clinical history of immunocompetence develop protective antibody levels to MMR and varicella and can receive these vaccines safely.