Background The CDC recommends that all children follow the primary immunization series vaccination schedule to prevent vaccine-preventable diseases. The treatment for acute lymphoblastic leukemia (ALL) targets lymphocytes, which are cells that play a role in memory retention for vaccine immunity. The purpose of this experiment is to determine whether there is loss of vaccine immunity in children treated for ALL and whether there is a difference between the high- risk ALL protocols and standard-risk ALL protocols. Understanding loss of immunity in children treated for ALL can help to establish reimmunization guidelines in order to protect survivors from vaccine-preventable diseases.

Methods This retrospective study consisted of chart reviews of 45 pediatric patients who are ALL survivors at Children's Hospital of Richmond. The results of hepatitis B, varicella, MMR, and Dtap titers drawn from these patients were compared to the general population using a one- proportion z-test. The ALL group was then divided into high-risk protocol and standard-risk protocol groups. Titers and lymphocyte enumeration panels were then compared between the two groups using a two-proportion z-test.

Results The results of this study showed that there was a significantly higher percentage of negative hepatitis B, varicella, MMR, and Dtap titers for the ALL group than in the general pediatric population (p<.01). However, there was no significant difference between children treated with high-risk protocols and standard-risk protocols (p = .42). The standard-risk group had 44% negative titers while the high-risk group had 53%. Additionally, the standard-risk group had 78% abnormal lymphocyte enumeration panel while the high-risk group had 86%.

Conclusion This study showed that children treated with chemotherapy for ALL lose immunity against vaccine preventable diseases and require reimmunization to protect them from future infection. Additionally, there is no significant statistical difference in immunity between the children treated with high-risk protocols vs standard-risk protocols. However, the percentage of negative titers and abnormal lymphocyte enumeration panels in the high-risk group was greater than the standard-risk group, so there may be some clinical significance. Therefore, routine revaccinations should be implemented after chemotherapy and children treated with high-risk protocols may require more follow-ups and precautions. Limitations of this study include small sample size and possible revaccinations at outside hospital systems. Future studies will look at the rate of lymphocyte recovery in standard vs high-risk protocol groups to further assess impacts of chemotherapy protocols on immunity.