Thread by @WHO

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

1⃣ the whole-microbe approach
2⃣ the subunit approach
3⃣ the genetic approach (nucleic acid vaccine)

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

1⃣ Inactivated vaccine (how flu & #polio vaccines are made)
2⃣ Live-attenuated vaccine
3⃣ 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 👉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.

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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 2⃣0⃣0⃣ vaccine candidates for #COVID19 being developed. Of these, at least 5⃣2⃣ candidate vaccines are in human trials and several others currently in phase I/II.

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