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What is an Experiment?

What is an Experiment?

An experiment is a planned activity carried out under controlled conditions. The purpose of an experiment is to investigate the relationship between two variables. When one variable causes change in another, we call the first variable the explanatory or independent variable. The affected variable is called the response or dependent variable. In a randomized experiment, the researcher manipulates values of the explanatory variable and measures the resulting changes in the response variable. The...

Data Collection by Experiments

Data Collection by Experiments

Data collection is a systematic method of obtaining, observing, measuring, and analyzing accurate information. An experimental study is a standard method of data collection that involves the manipulation of the samples by applying some form of treatment prior to data collection. It refers to manipulating one variable to determine its changes on another variable. The sample subjected to treatment is known as “experimental units.”
An example of the experimental method is a public...

Vaccinations

Vaccinations

Crossover Experiments

Crossover Experiments

Crossover experiments, also called the repeated-measurements design, is a study design in which all experimental units are exposed to all treatments in different periods. Crossover experiments are generally used in psychology, the pharmaceutical industry, agriculture, and medicine.
Crossover designs are performed even with smaller sample sizes since the samples can act as their controls. These are better than simple randomized trials since patients are exposed to all the treatments.

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A Suction Blister Protocol to Study Human T-cell Recall Responses In Vivo

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Emulating target trials of postexposure vaccines using observational data.

Christopher Boyer¹, Marc Lipsitch^1,2

¹Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health.

American Journal of Epidemiology

|September 13, 2024

Summary

Postexposure vaccination trials are challenging. This study defines target trials and shows how to emulate them using observational data, crucial for understanding vaccine effectiveness and timing.

Keywords:

effectiveness immortal time bias infectious disease monkeypox postexposure prophylaxis target trial vaccines

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Area of Science:

Epidemiology
Vaccinology
Clinical Trial Design

Background:

Postexposure vaccination can prevent or modify disease after pathogen exposure.
Logistical challenges hinder the practical implementation of postexposure vaccine trials.
Observational data analyses for postexposure vaccine effectiveness often lack clear links to trial methodologies.

Purpose of the Study:

To define target trials for postexposure vaccination.
To demonstrate the emulation of these target trials using observational data.
To highlight the role of incubation period and vaccination timing in trial design and emulation.

Main Methods:

Definition of several possible target trials for postexposure vaccination.
Development of methods to emulate target trials using observational data under specific conditions.
Specification of a postexposure vaccination protocol for mpox as a case study.
Step-by-step description for emulating trials using healthcare or contact tracing data.
Simulation to illustrate the benefits of the target trial approach.

Main Results:

Established conditions under which observational data can emulate target trials for postexposure vaccination.
Emphasized the critical importance of incubation period and vaccination timing in designing and emulating trials.
Provided a practical example for mpox postexposure vaccination emulation.
Demonstrated through simulation the advantages of the target trial emulation approach.

Conclusions:

Target trial emulation provides a framework to rigorously assess postexposure vaccination using observational data.
Understanding incubation periods and vaccination timing is essential for accurate trial design and emulation.
This approach can improve the estimation of postexposure vaccine effectiveness and optimal timing, overcoming logistical trial barriers.