Here are three main approaches to designing a #COVID19 vaccine:

the whole-microbe approach
the subunit approach
the genetic approach (nucleic acid vaccine)

Learn more http://bit.ly/3caqsDW 

The whole-microbe approach uses a whole virus/bacterium to design a vaccine. It can be divided in 3 categories:

Inactivated vaccine (how flu & #polio vaccines are made)
Live-attenuated vaccine
Viral vector vaccine (how #Ebola vaccine is made)

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The subunit approach uses the parts of the germ (or microbe) that triggers the immune system.

Most of the vaccines on the childhood schedule are subunit vaccines. Learn more http://bit.ly/3caqsDW 

The genetic approach (nucleic acid vaccine) uses a section of genetic material that provides the instructions for specific proteins, not the whole microbe.

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A nucleic acid vaccine delivers a specific set of instructions to our cells, either as DNA or mRNA, for them to make the specific protein that we want our immune system to recognize and respond to.

Learn more http://bit.ly/3caqsDW  https://twitter.com/WHO/status/1356208733769109505

Why are there so many vaccines in development

Typically, many vaccine candidates will be evaluated before any are found to be both safe & effective. Having lots of different vaccines in development increases the chances that there will be one or more successful vaccines.

As of December 2020, there are over vaccine candidates for #COVID19 being developed. Of these, at least candidate vaccines are in human trials and several others currently in phase I/II.

More details http://bit.ly/3caqsDW  https://twitter.com/WHO/status/1356238321274548225