A review of HIV surveillance, clinicalPertaining to or founded
on observation and treatment of participants, as distinguished
from theoretical or basic science. cohortIn epidemiologyThe
branch of medical science that deals with the study of incidence
and distribution and control of a disease in a population., a
group of individuals with some characteristics in common. A
cohort study is a special kind of clinical trialA clinical trial
is a research study to answer specific questions about vaccines
or new therapies or new ways of using known treatments. Clinical
trials are used to determine whether new drugs or treatments are
both safe and effective. Carefully conducted clinical trials are
the fastest and safest way to find treatments that work in
people. Trials are in four phases: Phase I tests a new drug or
treatment in a small group; Phase II expands the study to a
larger group of people; Phase III expands the study to an even
larger group of people; and Phase IV takes place after the drug
or treatment has b