Question: How do you create a vaccine?

Anabel Martinez Lyons answered on 24 Apr 2020:

Vaccines can be made in a few different ways (see below), but what they all have in common is that the original virus or bacteria is attenuated (scientific word for weakened to the point of NOT being dangerous) so that it cannot reproduce (make more of itself). When the vaccine is given to someone, it allows their body to create special immune system proteins called antibodies, that specifically recognise that virus or bacterium and allow us to react to the real thing better than if we didn’t have the vaccine.

Examples: One way to make a vaccine for a virus is to change the viral genes so that the virus replicates poorly. This is how the measles, mumps, rubella, and varicella vaccines are made.
Another way is to remove the viral genes completely so that the virus can’t replicate at all. This is how the polio vaccine is made. A third way is to use only a part of the virus or bacteria. This is how the hepatitis B vaccine is made. A fourth way specifically for bacteria is using a toxin that kills the bacteria so it can’t do any harm, used for infections like diphtheria, tetanus, and pertussis (whooping cough).