There are several methods to measure VE.

As already mentioned RCT can be used to measure VE (usually prelicensure phase 3a) or vaccine effectiveness (usually phase 4post licensure and increasingly prelicensure phase 3b)

Observational studies are assessments of VE in the field post-licensure, which  are are often undertaken in outbreak settings.

There are several methods which we will explore. They can be serological and/or epidemiological. Epidemiological methods include the rapid screening or case population method, cohort studies, family contact studies based on calculating household secondary attack rates, case-control methods and cross-sectional mthods such as EPI cluster sampling technique.