Once the pathogen is able to be grown in the laboratory, the following characteristics must be studied:
- Structure and behavior of the pathogen
- Route of entry into the host
- Interactions with cellular receptors
- Sites of replication
- Mechanism of disease initiation
Following this research, the body's immune response to the pathogen must be studied. Then, possible target antigens must be selected (if it is a subunit vaccine) that will be immunogenic, stable, induce an appropriate immune response, and be suitable for wide-scale production.
All of these steps in exploratory and pre-clinical testing require specialized laboratory methods, including a wide variety of cell culture, immunological, chemical, in silico (experimentation done on a computer), and animal testing. Continuing testing involves toxicity and potency testing. As you can see, the early development process involves many types of research laboratory methods which typically take years to perform. After that, pre-clinical and then clinical trials can be conducted, which also involve a lengthy process. The details of clinical trials will not be covered beyond what was previously stated.
