Should children with ALL be revaccinated after chemotherapy?

This study evaluated the outcomes of vaccination in children with acute lymphoblastic leukemia (ALL). This study found that children had less vaccine protection after chemotherapy.

Vaccines help the immune system recognize a pathogen using dead or weakened bacteria or viruses. Vaccines are not effective if someone’s immune system is weakened. Chemotherapy is a treatment for cancer that kills rapidly dividing cells and weakens the immune system. This is why vaccines are not usually recommended during chemotherapy. 

Vaccines protect against infections by triggering an immune response. The immune system makes molecules that recognize the pathogen. These molecules are called antibodies. For children with ALL, the risk of infection can last for years after finishing therapy. It is unclear if chemotherapy weakens protection from previous vaccines. 

This study included 78 children with ALL. All patients completed chemotherapy and had no signs of cancer. These patients were compared to 78 healthy children of similar ages (control group).

27% – 30% of patients with ALL had low levels of white blood cells. Significantly fewer had the pneumococcus vaccine (59% vs 79%) or all doses of the DTaP vaccine (41% vs 89%) compared to the control group. Patients with ALL also had significantly lower levels of antibodies to pneumococcus, pertussis, tetanus, and chickenpox.

Some children lost vaccine protection during chemotherapy. 48 patients had enough antibodies to protect them from chickenpox when they were diagnosed with ALL. Only 11 children continued to have vaccine protection after chemotherapy.

After blood tests, patients in the ALL group were vaccinated again. Antibody levels to pertussis, tetanus, and pneumococcus increased significantly after two months. A year after the DTaP vaccine, 97% of patients previously treated for ALL were protected against tetanus.

76% of patients had side effects after the DTaP-IPV-Hib vaccine, such as soreness. 9% had side effects that interfered with their daily activities. No serious side effects were reported.

This study found that children treated for ALL had lower levels of antibodies and that a second round of vaccinations was effective. The authors suggest that vaccination for children of all ages should be considered at least 4 months after chemotherapy.

Except for chickenpox, antibody levels were not measured before chemotherapy. This may bias the results.

If your child is in remission for ALL, ask their doctor about revaccination.