What is a candidate vaccine?

Answer 1

When new vaccines are being needed, they are created by drug companies that are approved to develop vaccines by the governments, who have pre-ordered the vaccines, making the drug companies want to manufacture them.

The health ministries of the countries and the World Health Organization, etc. help the drug companies find the strain of virus or type of bacteria or other microbe that will be the best match for the microbe that they are wanting to protect the public against with a vaccination. They determine what the best matched strains are that are circulating in the population or are expected to be circulating in the next flu season, and often provide the "seed stock" of that microbe to the drug companies.

Once the drug companies have grown the virus/bacteria, etc. and then killed or weakened it so it can not make anyone sick, they put it into a solution for injection. They then have a vaccine that is a candidate for the governments to approve so they can fulfill the orders they have received.

They present documentation to describe what it in it, how it was made, etc. to the government approval agencies. The drug companies and government agencies work together to conduct human trials and determine the safety and efficacy of the candidate vaccines.

Once the approval groups within the governments, such as the Food and Drug Administration (FDA) in the US and the European Medicines Agency (EMEA) in Europe/UK, have all the information about the candidate vaccines, they study the documentation and test results and select those candidate vaccines that they approve for use in their countries, and then the chosen vaccines are called approved vaccines instead of candidate vaccines.