COVID-19 Vaccine Janssen Description The Johnson and Johnson Janssen COVID-19 single-shot experimental vaccine leverages Janssen's AdVac and PER.C6® technologies. Janssen’s AdVac® vectors are based on a specific type of adenovirus, which has been genetically modified so that it can no longer replicate in humans and cause disease. Adenoviruses are a group of viruses that can cause the common cold. The AdVac® technology works by using an adenovirus as a vector (a carrier) of an antigen’s genetic code to mimic components of a pathogen (a bacterium, virus, or other disease-causing organisms). Antigens (components of a pathogen) are produced to mimic the pathogen without causing severe disease.