Reevaluating Immunization Delays Post Red Blood Cell Transfusion

Abstract

Abstract BACKGROUND Current Canadian guidelines recommend to delay the measles, mumps, rubella (MMR) and varicella live attenuated vaccines by 6 months following transfusion of unwashed red blood cells (RBC) due to potential interference by serum antibodies. Thus, patients chronically transfused with RBC commonly suffer from a delay or absence of MMR and varicella vaccination. Over the last decades, not only has RBC handling changed, but also fewer blood donors have had natural mumps, measles and rubella infections, resulting in lower blood antibody levels. The recommendations may thus be unfounded and outdated, and prevent valuable vaccination opportunities for children with frequent blood transfusions. OBJECTIVES The primary aim of this project was to determine MMR vaccination immunogenicity in patients chronically transfused with RBC. DESIGN/METHODS Medical charts were reviewed for vaccination and transfusion histories. MMR-specific antibodies were quantified in 25 paediatric patients who received both doses of the MMR vaccine at 12 and 18 months of age while they were on a chronic RBC transfusion program for sickle cell disease, B-thalassemia major, Diamond-Blackfan anemia or pyruvate kinase deficiency. There was no formal control group; long-term immunity rates in the literature are ≥90% for all MMR components. RESULTS Table 1 shows immunogenicity to MMR vaccine components. Delays between vaccination and serology testing averaged 5.9 years (0.3 to 15.8 years). CONCLUSION To the best of our knowledge, this is the first study designed to measure the effect of RBC transfusions on MMR vaccine immunogenicity. Although lower than the rates reported in the literature, the results suggest a high rate of immunogenicity to each component of the MMR vaccine in chronically transfused patients. Weighing the risks and benefits of disease prevention in a highly vulnerable population, a reevaluation of immunization delays post RBC transfusions is called for.