Methods for the estimation of direct and indirect vaccination effects by combining data from individual- and cluster-randomized trials

Both individually and cluster randomized study designs have been used for vaccine trials to assess the effects of vaccine on reducing the risk of disease or infection. The choice between individually and cluster randomized designs is often driven by the target estimand of interest (eg, direct versus total), statistical power, and, importantly, logistic feasibility. To combat emerging infectious disease threats, especially when the number of events from one single trial may not be adequate to obtain vaccine effect estimates with a desired level of precision, it may be necessary to combine information across multiple trials. In this article, we propose a model formulation to estimate the direct, indirect, total, and overall vaccine effects combining data from trials with two types of study designs: individual-randomization and cluster-randomization, based on a Cox proportional hazards model, where the hazard of infection depends on both vaccine status of the individual as well as the vaccine status of the other individuals in the same cluster. We illustrate the use of the proposed model and assess the potential efficiency gain from combining data from multiple trials, compared to using data from each individual trial alone, through two simulation studies, one of which is designed based on a cholera vaccine trial previously carried out in Matlab, Bangladesh.

[Insect community and its diversity in Mangrove forest at Yingluo Bay of Guangxi]

The insect community and its diversity in mangrove forest at Yingluo Bay of Guangxi were studied in 1995-1996. The results show that there were 195 insect species in the mangrove area, dominated by Crematogaster rogenhoferi, Camponotus tokioensis and Dichocrocris chorophanta. The diversity of insect community was higher in the inside beach than in the middle and outside beaches. Tides and windstorms were the important factors that decided the community composition levels. The principal component affecting the diversity was the species evenness in the inside, middle and outside beaches.

[Mucosal relief patterns in the colon (author's transl)]

Various types of mucosal relief patterns in the colon were classified on the basis of 270 double contrast examinations. Ten patterns were distinguished. In about 60% of examinations a normal pattern could be recognised, consisting of fine linear or reticular shadows. All other patterns depend on a substrate of morphological changes, which may result from surgical anastomoses, from stenoses or from inflammatory changes.

[Scintigraphy for doubtful vertebral fractures (author's transl)]

Fractures, particularly those of vertebral bodies, cannot always be demonstrated radiologically. The use of scintigraphy for this purpose is known but, in our opinion, this is not used sufficiently. Diagnosis of fractures by scintigraphy is almost 100% reliable. In the presence of degenerative changes in the spine, this is frequently the only method for differentiating between old and new fractures. By using the almost universally available substance 99mTc one has a cheap method with virtually no radiation dose. The earliest accumulation of 99mTc-MDP after fracture of a vertebral body was seen four hours after the trauma; absence of uptake three days after trauma excludes a fracture.

[Changes in the mucosal pattern of the colon in the early stages of ulcerative and granulomatous colitis (author's transl)]

By paying attention to the detailed relief pattern of the colonic mucosa on double contrast films, it is possible to recognise the early changes due to inflammatory colonic disease. The presence of a granular appearance suggests an early stage of ulcerative colitis; multiple small flecks of contrast, sometimes surrounded by a clear area, indicate aphthous ulcers in an early stage of Crohn's disease.