Financial Burden as a Potential Barrier to Vaccine Completion in Post-hematopoietic Stem Cell Transplant Patients in Japan

Introduction The administration of routine vaccinations to patients following hematopoietic stem cell transplantation (HSCT) is highly recommended. However, studies examining reasons for not completing vaccination in post-HSCT patients are lacking. Method We reviewed the medical records of patients who sought vaccination following HSCT from January 2012 to December 2018 at the Center for Infectious Diseases, Nara Medical University. Results Information regarding patients' backgrounds, administered vaccines, and reasons for not administering recommended vaccines was collected for the study. Thirty-five patients (22 men and 13 women) with a median time from HSCT to the first visit of 25 months were enrolled. Vaccine coverage was highest for diphtheria, tetanus, and acellular pertussis (DTaP) at 89% (31 patients), followed by 23-valent pneumococcal, measles/rubella/mumps, and Japanese encephalitis at 71% (25 patients), 71% (25 patients), and 63% (22 persons), respectively. However, vaccine coverage for hepatitis B, 13-valent pneumococcal, and Hib was low at 26% (three patients), 11% (four patients), and 40% (14 patients), respectively. The reason for not completing the recommended vaccination series was not provided for most cases; however, the economic barrier was cited for all vaccines. Discussion This study identified several cases in Japan where individuals stopped completing post-HSCT vaccinations due to financial constraints. Larger-scale studies may be necessary in Japan in the future for further investigation.

Safety of Immunization for Children with Immune Thrombocytopenia

Vaccine hesitancy is a common issue for children with immune thrombocytopenia (ITP) in China. The objective of this paper is to assess the immunization statuses of children with ITP, analyze the possible relationship between immunization and thrombocytopenia, and evaluate the safety of immunization after ITP remission. We included 186 children with an ITP history and followed up with them for two years after receiving re-immunization recommendations. The participants had an overall age-appropriate vaccine coverage of 57.9%. Vaccine-associated thrombocytopenia occurred in 99 (53.2%, 95% CI = 46.06-60.26) children ranging from 0 to 34 days following immunization, with 14 vaccines involved. One hundred and fifty-four (82.3%, 95% CI = 76.72-87.54) children were advised to restart immunization, whereas 32 (17.2%, 95% CI = 12.46-23.28) were advised to postpone partial or full vaccination. Following the follow-up, 150 (80.6%, 95% CI = 74.37-85.68) children completed the catch-up immunization, whereas 27 (14.5%, 95% CI = 10.17-20.30) partially completed it. Four patients with thrombocytopenia relapsed following the re-immunization. Incomplete catch-up immunization was related to the factors of chronic thrombocytopenia, vaccine-associated thrombocytopenia, and the relapse of ITP following re-immunization. ITP may occur after immunization with vaccines other than measles-containing vaccines. Re-immunization in children with ITP generally does not result in a relapse, regardless of whether the previous thrombocytopenia was vaccine-associated.

Immunogenicity of Catch-Up Immunization with Conventional Inactivated Polio Vaccine among Japanese Adults

Most Japanese adults are vaccinated twice with the Sabin trivalent oral polio vaccine. Booster vaccination is recommended for Japanese travelers to polio-endemic/high-risk countries. We assessed the catch-up immunization of healthy Japanese adults aged ≥20 years with two doses of standalone conventional inactivated polio vaccine (cIPV). Immunogenicity was evaluated by serum neutralization titers (pre-booster vaccination, 4-6 weeks after each vaccination) against type 1, 2, and 3 poliovirus strains. The participants were 61 healthy Japanese adults (26 men/35 women; mean age ± standard deviation age 35.8 ± 8.0 years). Seropositivity rates (percentage of participants with anti-poliovirus antibody titers ≥1:8) pre-vaccination were 88.5%, 95.1%, and 52.5% for Sabin strains (type 1, 2, and 3); 72.1%, 93.4%, and 31.1% for virulent poliovirus strains (type 1: Mahoney; type 2: MEF-1; and type 3: Saukett); and 93.4%, 93.4%, 93.4%, and 88.5% for type 2 vaccine-derived poliovirus strains (SV3128, SV3130, 11,196, and 11,198). After one cIPV dose, all seropositivity rates increased to 98.4-100.0%. After two cIPV doses, the seropositivity rates reached 100% for all strains. cIPV was well tolerated, with no safety concerns. Catch-up immunization with standalone cIPV induced robust immune responses in Japanese adults, indicating that one booster dose boosted serum-neutralizing antibodies to many strains.