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In 2008, the number of pertussis cases increased substantially among Japanese adolescents, despite high coverage with acellular pertussis vaccine (DTaP). This study examined the effectiveness of DTaP vaccine in the routine immunization program in Japan. Between April 2009 and October 2012, we conducted a multicenter, case-control study, and compared the history of DTaP vaccination between 55 newly diagnosed pertussis cases and 90 age- and sex-matched controls. DTaP vaccine history was obtained by a self-administered questionnaire completed by their parents or guardians. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) of vaccination for development of pertussis. DTaP vaccination of ≥1 dose revealed a significantly lower OR for pertussis (OR = 0.20, 95%CI, 0.04–0.97), and the OR of complete vaccination (4 doses) was 0.22 (0.04–1.05). Even after limiting subjects to those whose vaccination status could be confirmed by the immunization records, the negative associations were observed. The decreasing ORs of 4-dose vaccinees remained, even among subjects who had received the fourth dose ≥9.2 years earlier (OR = 0.11, 95%CI, 0.01–1.02). In conclusion, DTaP vaccination had a preventive effect for pertussis. Effectiveness was observed even 9 or more years after the final dose. [ABSTRACT FROM AUTHOR]

Although anaphylaxis is an extremely rare vaccine-associated adverse event, it occurred in young children following administration of the 2011/12 seasonal split influenza vaccine, which contained 2-phenoxyethanol as the preservative. These children had high levels of IgE antibodies against influenza vaccine components. We herein investigated why these children were sensitized. One hundred and seventeen series of serum samples were obtained immediately before, and one month after the first and second immunizations with the HA split vaccine of 2011/12. Forty-two sequential serum samples were collected in the acute and convalescent phases (2 and 4 weeks) after natural infection with H1N1 Pdm in 2009. IgE antibodies developed following the vaccination of young children with seasonal split vaccines, whereas no significant IgE response was observed following natural infection with H1N1 Pdm 2009. The prevalence of IgE antibodies was not influenced by outbreaks of H1N1 Pdm. Repeated immunization with the HA split vaccine induced IgE sensitization against the influenza vaccine irrespective of the H1N1, H3N2, or B influenza subtypes. The reasons why anaphylaxis only occurred in recipients of the influenza vaccine containing 2-phenoxyethanol are still being investigated, and the size distribution of antigen particles may have shifted to a slightly larger size. Since the fundamental reason was IgE sensitization, current split formulation for the seasonal influenza vaccine needs to be reconsidered to prevent the induction of IgE sensitization. [ABSTRACT FROM AUTHOR]