Vaccine
Volume 33, Issue 12, Pages 1419-1506 (17 March 2015)
http://www.sciencedirect.com/science/journal/0264410X/33/12

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Discussion
Should close contacts of returning travellers with typhoid fever be protected by vaccination?
Pages 1419-1421
A. Kantele
Abstract
Increasing international travel to areas endemic for typhoid fever correlates with increased risk for travellers to contract the disease. At home, the acutely ill/convalescent patients may pose some risk to their close contacts. In Finland an unofficial guideline suggests vaccination for close contacts of patients with acute typhoid fever; in other developed countries, routine typhoid vaccinations are only recommended to contacts of chronic carriers. This paper discusses the possibilities and limitations of prophylactic/post-exposure typhoid vaccination for contacts of patients with acute disease.

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Brief report
Greater freedom of speech on Web 2.0 correlates with dominance of views linking vaccines to autism
Pages 1422-1425
Anand Venkatraman, Neetika Garg, Nilay Kumar
Abstract
Introduction
It is suspected that Web 2.0 web sites, with a lot of user-generated content, often support viewpoints that link autism to vaccines.
Methods
We assessed the prevalence of the views supporting a link between vaccines and autism online by comparing YouTube, Google and Wikipedia with PubMed. Freedom of speech is highest on YouTube and progressively decreases for the others.
Results
Support for a link between vaccines and autism is most prominent on YouTube, followed by Google search results. It is far lower on Wikipedia and PubMed. Anti-vaccine activists use scientific arguments, certified physicians and official-sounding titles to gain credibility, while also leaning on celebrity endorsement and personalized stories.
Conclusions
Online communities with greater freedom of speech lead to a dominance of anti-vaccine voices. Moderation of content by editors can offer balance between free expression and factual accuracy. Health communicators and medical institutions need to step up their activity on the Internet.

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Review
Comparing vaccines: A systematic review of the use of the non-inferiority margin in vaccine trials
Review Article
Pages 1426-1432
R. Donken, H.E. de Melker, N.Y. Rots, G. Berbers, M.J. Knol
Abstract
Background
Non-inferiority (NI) randomized controlled trials (RCTs) aim to demonstrate that a new treatment is no worse than a comparator that has already shown its efficacy over placebo within a pre-specified margin. However, clear guidelines on how the NI margin should be determined are lacking for vaccine trials. A difference (seroprevalence/risk) of 10% or a geometric mean titre/concentration (GMT) ratio of 1.5 or 2.0 in antibody levels is implicitly recommended for vaccine trials. We aimed to explore which NI margins were used in vaccine RCTs and how they were determined.
Methods
A systematic search for NI vaccine RCTs yielded 177 eligible articles. Data were extracted from these articles using a standardized form and included general characteristics and characteristics specific for NI trials. Relations between the study characteristics and the NI margin used were explored.
Results
Among the 143 studies using an NI margin based on difference (n = 136 on immunogenicity, n = 2 on efficacy and n = 5 on safety), 66% used a margin of 10%, 23% used margins lower than 10% (range 1–7.5%) and 11% used margins larger than 10% (range 11.5–25%). Of the 103 studies using a NI margin based on the GMT ratio, 50% used a margin of 0.67/1.5 and 49% used 0.5/2.0. As observed, 85% of the studies did not discuss the method of margin determination; and 19% of the studies lacked a confidence interval or p-value for non-inferiority.
Conclusion
Most NI vaccine RCTs used an NI margin of 10% for difference or a GMT ratio of 1.5 or 2.0 without a clear rationale. Most articles presented enough information for the reader to make a judgement about the NI margin used and the conclusions. The reporting on the design, margins used and results of NI vaccine trials could be improved; more explicit guidelines may help to achieve this end.

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Modeling the durability of ZOSTAVAX® vaccine efficacy in people ≥60 years of age
Original Research Article
Pages 1499-1505
Xiaoming Li, Jane H. Zhang, Robert F. Betts, Vicki A. Morrison, Ruifeng Xu, Robbin F. Itzler, Camilo J. Acosta, Erik J. Dasbach, James M. Pellissier, Gary R. Johnson, Ivan S.F. Chan
Abstract
Since 2006, the vaccine, ZOSTAVAX®, has been licensed to prevent herpes zoster. Only limited clinical follow-up data are available to evaluate duration of protection, an important consideration when developing HZ vaccination policy recommendations. Four Poisson regression models were developed based on an integrated analysis of data from the Shingles Prevention Study and its Short Term Persistence extension to estimate the effects of years-since-vaccination and chronological-age on vaccine efficacy among people ≥60 years old. The models included number of HZ cases parsed into categories by chronological-age and time-since-vaccination as the dependent variable with different explanatory variables in each model. In all models, the interaction between vaccine-group and chronological-age was statistically significant indicating that vaccine efficacy decreases with the expected effects of advancing age but the interaction between vaccine-group and time-since-vaccination was not statistically significant indicating that much of the reduction in vaccine efficacy over time-since-vaccination can be explained by increasing age.