Thread by @petermbenglish

"Covid vaccine: First 'milestone' vaccine offers 90% protection"
bbc.co.uk/news/health-54…

JamesTGallagher

This is good news. Some thoughts about Covid-19 vaccinations and mRNA vaccines in particular.
2/11

The R0 for Covid-19 is about 2.5.

If it were 3 you'd have to get 2 out of every three people who would otherwise have caught it immune, so they don't catch it and pass it on. If it's less, you have to get fewer people immune in order to achieve population (herd) immunity .
3/11

This is much easier than, for example, measles, where R0 is >=15 - so you have to get >14/15 people immune to achieve population immunity.

So there is a pretty good chance of getting population immunity, even if the vaccine is only 90% effective. But…
4/11

The caveat, of course, is - does the vaccine prevent infection, or just illness?
5/11

If people, while protected from significant illness, can still become infected - and able to transmit the virus to others - then we won't get population immunity, just individual protection (which is still worthwhile).
6/11

My guess is that it probably will prevent infection. It seems to stimulate both an antibody, and a T-cell response. But the data probably won't be able to PROVE that for some time, so they won't be able to claim it.
7/11

It's also good news for vaccination and immune therapy more broadly.

We don't, currently, have any RNA or DNA vaccines in use in humans; yet they have huge potential.
8/11

ONce the process and cold chains are established, it is quick, easy, and relatively safe to develop new vaccines, or to fine-tune existing DNA/RNA vaccines by modifying the genetic sequences.
9/11

This will open the door to more rapid development of affordable vaccines against other conditions. Who knows, it might even help us develop therapeutic vaccines that will stimulate the immune system to eradicate latent (eg HPV or TB) infection.
10/11

It also has potential for other immune therapies such as cancer "vaccines".

So this is very good news, both wrt Covid-19, and more widely for the future of vaccines and immune therapies.
11/11

fao @jkaffash
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Here's the report from Pfizer:

pfizer.com/news/press-rel…