Tick-borne Encephalitis Vaccine Failures: A 10-year Retrospective Study Supporting the Rationale for Adding an Extra Priming Dose in Individuals Starting at Age 50 Years.

BACKGROUND: Southern Sweden is endemic for tick-borne encephalitis (TBE), with Stockholm County as one of the high-risk areas. Our aim in this study was to describe cases of vaccine failures and to optimize future vaccination recommendations. METHODS: Patients with TBE were identified in the notification database at the Department of Communicable Disease Control and Prevention in Stockholm County during 2006-2015. Vaccine failure was defined as TBE despite adherence to the recommended vaccination schedule with at least 2 doses. Clinical data were extracted from medical records. RESULTS: A total of 1004 TBE cases were identified, 53 (5%) were defined as vaccine failures. In this latter group, the median age was 62 years (6-83). Forty-three (81%) patients were aged >50 years and 2 were children. Approximately half of the patients had comorbidities, with diseases affecting the immune system accounting for 26% of all cases. Vaccine failures following the third or fourth vaccine dose accounted for 36 (68%) of the patients. Severe and moderate TBE disease affected 81% of the cases. CONCLUSIONS: To our knowledge, this is the largest documented cohort of TBE vaccine failures. Vaccine failure after 5 TBE vaccine doses is rare. Our data provide rationale for adding an extra priming dose to those aged ≥50 years.

Modulation of innate immune response to mRNA vaccination after SARS-CoV-2 infection or sequential vaccination in humans.

mRNA vaccines are likely to become widely used for the prevention of infectious diseases in the future. Nevertheless, a notable gap exists in mechanistic data, particularly concerning the potential effects of sequential mRNA immunization or preexisting immunity on the early innate immune response triggered by vaccination. In this study, healthy adults, with or without documented prior SARS-CoV-2 infection, were vaccinated with the BNT162b2/Comirnaty mRNA vaccine. Prior infection conferred significantly stronger induction of proinflammatory and type I IFN-related gene signatures, serum cytokines, and monocyte expansion after the prime vaccination. The response to the second vaccination further increased the magnitude of the early innate response in both study groups. The third vaccination did not further increase vaccine-induced inflammation. In vitro stimulation of PBMCs with TLR ligands showed no difference in cytokine responses between groups, or before or after prime vaccination, indicating absence of a trained immunity effect. We observed that levels of preexisting antigen-specific CD4 T cells, antibody, and memory B cells correlated with elements of the early innate response to the first vaccination. Our data thereby indicate that preexisting memory formed by infection may augment the innate immune activation induced by mRNA vaccines.

Qdenga® - A promising dengue fever vaccine; can it be recommended to non-immune travelers?

Qdenga® has been approved by the European Medicines Agency (EMA) for individuals > 4 years of age and for use according to national recommendations. The vaccine shows high efficacy against virologically confirmed dengue and severe dengue in clinical studies on 4-16-year old's living in endemic areas. For individuals 16-60 years old only serological data exists and there is no data for individuals > 60 years. Its use as a travel vaccine is still unclear. We present the studies behind the approval and the recommendations for travelers as issued by the Swedish Society for Infectious Diseases Physicians.

An extra priming dose of hepatitis A vaccine to adult patients with rheumatoid arthritis and drug induced immunosuppression - A prospective, open-label, multi-center study.

BACKGROUND: Previous studies have indicated that a pre-travel single dose of hepatitis A vaccine is not sufficient as protection against hepatitis A in immunocompromised travelers. We evaluated if an extra dose of hepatitis A vaccine given shortly prior to traveling ensures seroconversion. METHOD: Patients with rheumatoid arthritis (n = 69, median age = 55 years) treated with Tumor Necrosis Factor inhibitor(TNFi) and/or Methotrexate (MTX) were immunized with two doses of hepatitis A vaccine, either as double dose or four weeks apart, followed by a booster dose at six months. Furthermore, 48 healthy individuals, median age = 60 years were immunized with two doses, six months apart. Anti-hepatitis A antibodies were measured at 0, 1, 2, 6, 7 and 12 months. RESULTS: Two months after the initial vaccination, 88% of the RA patients had protective antibodies, compared to 85% of the healthy individuals. There was no significant difference between the two vaccine schedules. At twelve months, 99% of RA patients and 100% of healthy individuals had seroprotective antibodies. CONCLUSION: An extra priming dos of hepatitis A vaccine prior to traveling offered an acceptable protection in individuals treated with TNFi and/or MTX. This constitutes an attractive pre-travel solution to this vulnerable group of patients.