Monthly Archives: January 2017

Do Antibody Responses to the Influenza Vaccine Persist Year-Round in the Elderly? A Systematic Review and Meta-Analysis


Introduction: The influenza vaccine is less immunogenic in older than younger adults, and the duration of protection is unclear. Determining if protection persists beyond a typical seasonal epidemic is important for climates where influenza virus activity is year-round.

Methods: A systematic review protocol was developed and registered with PROSPERO [CRD42015023847]. Electronic databases were searched systematically for studies reporting haemagglutination-inhibition (HI) titres 180-360days following vaccination with inactivated trivalent seasonal influenza vaccine, in adults aged ⩾65years. Geometric mean titre (GMT) and seroprotection (HI titre ⩾1:40) at each time point was extracted. A Bayesian model was developed of titre trajectories from pre-vaccination to Day 360. In the meta-analysis, studies were aggregated using a random-effects model to compare pre-vaccination with post-vaccination HI titres at Day 21-42 (‘seroconversion’), Day 180 and Day 360. Potential sources of bias were systematically assessed, and heterogeneity explored.

Results: 2864 articles were identified in the literature search, of which nineteen met study inclusion/exclusion criteria. Sixteen studies contained analysable data from 2565 subjects. In the Bayesian model, the proportion of subjects seroprotected increased from 41-51% pre-vaccination to 75-78% at seroconversion. Seroprotection subsequently fell below 60% for all serotypes by Day 360: A/H1 42% (95% CI 38-46), A/H3 59% (54-63), B 47% (42-52). The Bayesian model of GMT trajectories revealed a similar pattern. By Day 360, titres were similar to pre-vaccination levels. In the meta-analysis, no significant difference in proportion of subjects seroprotected, 0 (-0.11, 0.11) or in log2GMT 0.30 (-0.02, 0.63) was identified by Day 360 compared with pre-vaccination. The quality of this evidence was limited to moderate on account of significant participant dropout.

Conclusions: The review found consistent evidence that HI antibody responses following influenza vaccination do not reliably persist year-round in older adults. Alternative vaccination strategies could provide clinical benefits in regions where year-round protection is important.

Citation: Young, B., Zhao, X., Cook, A. R., Parry, C. M., Wilder-Smith, A., & I-Cheng, M. C. (2017). Do antibody responses to the influenza vaccine persist year-round in the elderly? A systematic review and meta-analysis. Vaccine35(2), 212-221.

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Diabetes, cardiac disorders and asthma as risk factors for severe organ involvement among adult dengue patients: A matched case-control study


Progression to severe organ involvement due to dengue infection has been associated with severe dengue disease, intensive care treatment, and mortality. However, there is a lack of understanding of the impact of pre-existing comorbidities and other risk factors of severe organ involvement among dengue adults. The aim of this retrospective case-control study is to characterize and identify risk factors that predispose dengue adults at risk of progression with severe organ involvement. This study involved 174 dengue patients who had progressed with severe organ involvement and 865 dengue patients without severe organ involvement, matched by the year of presentation of the cases, who were admitted to Tan Tock Seng Hospital between year 2005 and 2008. Age group of 60 years or older, diabetes, cardiac disorders, asthma, and having two or more pre-existing comorbidities were independent risk factors of severe organ involvement. Abdominal pain, clinical fluid accumulation, and hematocrit rise and rapid platelet count drop at presentation were significantly associated with severe organ involvement. These risk factors, when validated in a larger study, will be useful for triage by clinicians for prompt monitoring and clinical management at first presentation, to minimize the risk of severe organ involvement and hence, disease severity.

Citation: Pang, J., Hsu, J. P., Yeo, T. W., Leo, Y. S., & Lye, D. C. (2017). Diabetes, cardiac disorders and asthma as risk factors for severe organ involvement among adult dengue patients: A matched case-control study. Scientific reports7(1), 1-10.

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