Influenza vaccine effectiveness against influenza A in children based on the results of various rapid influenza tests in the 2018/19 season.

During influenza epidemics, Japanese clinicians routinely conduct rapid influenza diagnostic tests (RIDTs) in patients with influenza-like illness, and patients with positive test results are treated with anti-influenza drugs within 48 h after the onset of illness. We assessed the vaccine effectiveness (VE) of inactivated influenza vaccine (IIV) in children (6 months-15 years old, N = 4243), using a test-negative case-control design based on the results of RIDTs in the 2018/19 season. The VE against influenza A(H1N1)pdm and A(H3N2) was analyzed separately using an RIDT kit specifically for detecting A(H1N1)pdm09. The adjusted VE against combined influenza A (H1N1pdm and H3N2) and against A(H1N1)pdm09 was 39% (95% confidence interval [CI], 30%-46%) and 74% (95% CI, 39%-89%), respectively. By contrast, the VE against non-A(H1N1)pdm09 influenza A (presumed to be H3N2) was very low at 7%. The adjusted VE for preventing hospitalization was 56% (95% CI, 16%-77%) against influenza A. The VE against A(H1N1)pdm09 was consistently high in our studies. By contrast, the VE against A(H3N2) was low not only in adults but also in children in the 2018/19 season.

Induction of immune tolerance to platelet antigen by short-term thrombopoietin treatment in a mouse model of immune thrombocytopenia.

Immune thrombocytopenia (ITP) is an autoimmune disorder caused by IgG anti-platelet autoantibodies. Thrombopoietin (TPO) receptor agonists are highly effective in inducing the recovery of platelet counts in ITP patients. Although these agents are thought to promote platelet production without affecting the autoimmune pathogenesis of the disease, a small subset of ITP patients exhibits sustained platelet recovery after treatment termination. To investigate mechanisms involved in this sustained recovery, we evaluated the effects of short-term TPO treatment using a mouse ITP model generated by Foxp3(+) T regulatory cell (Treg) depletion. After treatment, platelet recovery was sustained, along with complete suppression of both anti-platelet autoantibody production and T-cell responses to platelet autoantigens. TPO treatment also promoted the peripheral induction of Foxp3(+) Tregs in conjunction with elevated circulating TGF-ß levels. In summary, thrombopoietic agents are capable of inducing immune tolerance to platelet autoantigens, thereby suppressing the autoimmune pathogenesis of ITP.