The use of antibiotics has promoted antibiotic resistance, which is a major global threat to the treatment of bacterial infections. The bacteria which survive are the ones which are resistance to an antibiotic. These are the bacteria which will survive to infect the next person.

The situation is much the same with vaccines which act against viral infection.

Vaccines which do not sterilise the body of a virus will leave some viral particles alive. It is these surviving viruses, which are not killed by vaccine induced antibodies, that survive to reproduce. This is why vaccines can lead to the evolution of new variants of a virus. In other words, the virus must evolve to avoid vaccine induced immunity.

It is also noted that repeated vaccination can stimulate the T suppressor lymphocytes that actually inhibit the immune response.

We discuss the difference between mucosal and systemic immunity. Active and passive immunity are discussed, active immunity is generated by antigen exposure.

Professor Clancy also clarifies my thinking on point mutations versus recombinant new variants. This difference accounts for viral genetic shift and drift. We note that shifts are associated by significant immune escape. Fortunately, these genetic changes have so far led to covid viruses which cause less severe disease, while still being very transmissible. This has reduced serious illness and deaths, while promoting widespread natural immunity.