A vaccine is a biological preparation which is used to establish or improve immunity to a particular disease. Vaccines can be prophylactic (e.g. to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen), or therapeutic (e.g. vaccines against cancer are also being investigated).

There are many types of vaccines. Vaccines for virus infections can be live viruses that are killed, live-attenuated viruses, subunit or protein components of the virus, recombinant DNA and virus like particles (VLPs). VLPs are a new, potent type of vaccine which mimics the native virus structure, yet avoiding the safety issues with live-killed or live-attenuated viral vaccines. VLPs are empty virus particles that are stripped of genetic information, thereby making them extremely safe.

Lentigen is presently developing several vaccine candidates including VLP vaccines for pandemic influenza and Hepatitis C virus infection.