Oxford’s ChAdOx1- nCoV-19 Vaccine

By Nana Dadzie Ghansah

Using Adenoviruses as viral vectors (Borrowed from From he Native Antigen Company)

Traditionally, to create a vaccine against a disease-causing pathogen, a weakened version of the pathogen (called live-attenuated) or an inactivated or killed-off version of that pathogen was used. When these versions of a pathogen are introduced into the human body (vaccination), they do not cause disease but lead to the adaptive immune system producing antibodies that for long periods of time, protect from the disease caused by that pathogen.

Vaccines that use attenuated pathogens include those against smallpox, measles, mumps, yellow fever, to mention a few. Inactivated pathogens are used in the vaccines against diseases like cholera, pertussis, and the oral Salk polio vaccine.

Though using a live attenuated pathogen leads to a stronger immune reaction and thus longer-lasting immunity than using an inactivated one, these live attenuated viruses can gain their virulence back after entering the human body and lead to disease.

This was seen with the first smallpox vaccines. The initial smallpox vaccine used a live attenuated version of the vaccinia virus that Edward Jenner used over 200 years ago. This is another virus from the poxvirus family. In its attenuated form, it usually did not cause severe disease in humans (rash and fever) and thus, was used as the predominant virus for the…