Monoclonal antibodies are designed to target a very specific part of a virus or bacterium, and are carefully selected and tested for effectiveness.
Polyclonal antibodies are a mixture of many different antibodies—some good, and some not so good—that are produced as part of the body’s response to a foreign substance. Convalescent plasma (plasma that is taken from someone who has recovered from an infection) is an example of a substance that contains polyclonal antibodies.