Seroconversion status after single dose and double doses of varicella vaccination in children with leukemia

Vaccine Immunity in Children After Hematologic Cancer Treatment: A Retrospective Single-center Study

BACKGROUND

Children lose their vaccine-induced protection and are particularly vulnerable to vaccine-preventable diseases after chemotherapy. However, revaccination guidelines are heterogeneous, and there is often a lack of revaccination post-treatment.

AIMS

We conducted a retrospective study of children with hematologic cancer to evaluate vaccine immunity before and after the end of treatment and to determine whether the current institutional revaccination program based on vaccine serology results was followed and effective.

MATERIALS AND METHODS

Data of all children treated by chemotherapy between April 2015 and July 2021 were extracted from hospital medical records for analysis. Serum antibody levels and time of vaccination were evaluated for diphtheria, tetanus, Streptococcus pneumoniae , Haemophilus influenzae type b (Hib), measles, varicella, and hepatitis B.

RESULTS

We included 31 patients (median age, 9 years). At cancer diagnosis, 90% of children were protected against tetanus, diphtheria, and measles; 65% to 67% were protected against pneumococcus and varicella; and 25% against hepatitis B. At the end of chemotherapy, 67% to 71% of patients were protected against tetanus, varicella, and measles; 40% remained protected against hepatitis B; and 27% to 33% against pneumococcus and diphtheria. Patients were revaccinated at various times after the end of treatment but not systematically. During the first-year post-treatment, 20% to 25% of children remained unprotected against pneumococcus, measles, and hepatitis B, one third against diphtheria, but all were protected against tetanus and varicella.

CONCLUSIONS

An effective individualized vaccination program post-cancer based on serology results should be accompanied by an appropriate serology tracking method and follow-up to assess if booster doses are necessary. Our study supports vaccinating all children with a dose of the 13-valent pneumococcal conjugate at cancer diagnosis and at 3 months post-treatment with the combined diphtheria-tetanus-acellular pertussis/poliomyelitis vaccine/hepatitis B virus plus or minus Hib and 13-valent pneumococcal conjugate and meningococcal vaccine, including measles/mumps/rubella-varicella zoster virus vaccine if good immune reconstitution is present.

A prospective multicenter study on varicella-zoster virus infection in children with acute lymphoblastic leukemia

BACKGROUND AND METHODS

The study evaluated prognostic factors associated with varicella-zoster virus (VZV) infection and mortality in children with acute lymphoblastic leukemia (ALL) using data from the multicenter Chinese Children's Cancer Group ALL-2015 trial.

RESULTS

In total, 7,640 patients were recruited, and 138 cases of VZV infection were identified. The incidence of VZV infection was higher in patients aged ≥ 10 years (22.5%) and in patients with the E2A/PBX1 fusion gene (11.6%) compared to those aged < 10 years (13.25%, P = 0.003) or with other fusion genes (4.9%, P = 0.001). Of the 10 deaths in children with ALL and VZV infection, 4 resulted from VZV complications. The differences between groups in the 5-year overall survival, event-free survival, cumulative recurrence, and death in remission were not statistically significant. The proportion of complex infection was higher in children with a history of exposure to someone with VZV infection (17.9% vs. 3.6%, P = 0.022).

CONCLUSION

VZV exposure was associated with an increased incidence of complex VZV infection and contributed to VZV-associated death in children with ALL.

Varicella zoster immune status in children treated for acute leukemia

Children treated for acute leukemia are at increased risk of severe infection with varicella zoster virus (VZV). We studied the VZV sero-status of children with acute leukemia prior to starting chemotherapy and after completion of chemotherapy. VZV sero-status was assessed using time resolved fluorescence immunoassay (TRFIA) before starting treatment and 6 months after completion of treatment. Prior to starting treatment for acute leukemia, a significant proportion of children (35%) are VZV seronegative. On completion of treatment most patients maintained protective VZV antibody levels; however, 35% had reduced/loss VZV antibody to a level considered non-protective and susceptible to VZV infection.

Guidelines on vaccinations in paediatric haematology and oncology patients

OBJECTIVE

Vaccinations are the most important tool to prevent infectious diseases. Chemotherapy-induced immune depression may impact the efficacy of vaccinations in children.

PATIENTS AND METHODS

A panel of experts of the supportive care working group of the Italian Association Paediatric Haematology Oncology (AIEOP) addressed this issue by guidelines on vaccinations in paediatric cancer patients. The literature published between 1980 and 2013 was reviewed.

RESULTS AND CONCLUSION

During intensive chemotherapy, vaccination turned out to be effective for hepatitis A and B, whilst vaccinations with toxoid, protein subunits, or bacterial antigens should be postponed to the less intensive phases, to achieve an adequate immune response. Apart from varicella, the administration of live-attenuated-virus vaccines is not recommended during this phase. Family members should remain on recommended vaccination schedules, including toxoid, inactivated vaccine (also poliomyelitis), and live-attenuated vaccines (varicella, measles, mumps, and rubella). By the time of completion of chemotherapy, insufficient serum antibody levels for vaccine-preventable diseases have been reported, while immunological memory appears to be preserved. Once immunological recovery is completed, usually after 6 months, response to booster or vaccination is generally good and allows patients to be protected and also to contribute to herd immunity.

Varicella vaccines

BACKGROUND

Varicella zoster virus infection (VZV) is widespread and clinically important as the cause of varicella pneumonitis and meningoencephalitis (a complication of primary infection/zoster) and post-herpetic neuralgia (a complication of zoster/secondary infection). The use of live-attenuated varicella vaccine to reduce the burden of these diseases has been established in many countries for a number of years.

SOURCES OF DATA

Original papers and review articles including guidelines and recommendations by the American Academy of Paediatrics Committee on Infectious Diseases, the Advisory Committee on Immunization Practices and EuroSurveillance.

AREAS OF AGREEMENT

Immunoassay of VZV IgG by enzyme immunosorbent assay is used as a surrogate marker for previous primary infection or successful immunization. Patients who have had natural primary infection do not require vaccination against varicella. Live VZV vaccines are safe and effective at protecting against disease caused by VZV. To ensure long-term protection, a two-dose immunization regime is strongly recommended, due to significant waning of protection following a single dose. Universal two-dose immunization has been shown to be cost-effective in Western temperate countries. In many countries, routine vaccination of children is recommended but, due to cost, often not provided by universal programmes. Cost-effectiveness of a universal programme will be determined by the baseline rate of severe varicella disease.

AREAS OF CONTROVERSY

No international consensus exists: measurement of VZV immunity or cost-effectiveness of introducing VZV vaccination to a country. Decisive factors will include the pre-vaccination burden of VZV-associated disease.