It can’t be done effectively during exponential growth at the current rate: there simply aren’t enough identified recovered patients to supply serum to the currently sick patients. If the exponential rate decreases a bit, maybe.

FWIW, it seems at least plausible to me that a recovered patient who was treated with serum may not generate as many protective antibodies as a naturally recovered patient. For example, Rh antibodies are used during pregnancy specifically to prevent an immune response. I don’t know if this would apply to COVID-19 or if giving serum only after symptoms become severe would prevent this outcome.

See my reply to your original comment. Exponential growth isn’t a valid reason for this to not work. The factor of recovered vs currently Ill patients is constant, exponential growth or not. This factor may be high and I assume this is what you mean but given the (relatively small) percentage of critically ill and the fact that some countries are further along this is not a clear disqualifying argument against serum.

Not a doctor, but AFAIK its not considered safe enough. There are quite a few possible side-effects from using some of the mentioned medication, ranging from diarrhea to QT interval changes that could induce cardiac arrest.

One thing I couldn't find a source for is how many donors could potentially help how many people. Is it 1 to 1? 1 donor can help multiple people? Or one patient needs the amount of multiple donors?

The article I read on serum suggested that one donor could help two people. No URL, I’m afraid.

That's exactly it. If the virus is exploding exponentially the number of recovered cases is a tiny, tiny fraction of the active ones. This treatment doesn't work until things are under control, basically.

But if the death rate is "only" 1 in 10 (approximately) then doesn't that mean there are ~9 survivors for every terminally ill patient? It doesn't seem like the number of survivors would be the limiting factor here.

No, because the virus takes time. Survivors aren't "survivors" until they've recovered, so they reflect the people who "would have been" critical cases maybe 10-15 days ago. But 10-15 days ago the number of cases was (depending on which doubling statistic you use) 4x-32x smaller than what it is today.

Exponential growth messes everything up, basically. All our intuition about how things work tends to be wrong in subtle ways.

e^(ct)/e^(c(t - 14days)) = e^(c*14days) = k = constant, with c the growth rate. While you are right that, in an exponential growth scenario, the number of recovered cases is smaller than the number of currently active cases, the factor is proportional to the growth rate which is worst case constant, but likely going down over time due to quarantine measures. As such we have theoretically enough recovered cases if n_infected/n_critical > k. For the most critical age group an estimated 10% of infected require ICU care [1]. Thus we need k < 10. With a 1:2 ratio for serum we get k < 20. Likely not everyone will donate though and constant factors in this equation will end up mattering but the exponential nature does not kill the idea in the manner you indicate. However, it still requires scaling production exponentially. This is true for all other drugs as well though.

[1] https://www.imperial.ac.uk/media/imperial-college/medicine/s...

You don’t need 80-year-old serum to treat an 80-year-old patient.

I think trials for this are beginning - I suspect it would have been a hard thing to include in the WHO trial, as a hospital needs to be fairly sophisticated to be able to coordinate plasma retrieval and cleaning locally (vs buying RBCs from a local supplier).

I’m curious /excited to rare how this dynamic changes once we get serological tests online. Maybe all of the mild cases amongst youth can give enough serum to treat the harder hit individuals.

Here’s a recent discussion about serum:

https://www.globalhealthnow.org/2020-03/covid-19s-stop-gap-s...

And the linked study:

https://www.jci.org/articles/view/138003

1. Too expensive 2. Safety unknown at large scale 3. Production facilities insufficient

And many more reasons...

Do you have a source for this? Interesting if true!

1. Where are the high costs coming from? Distribution? Storage? People? Most of these seem shared for other drugs.

2. Blood transfusion seems to be one of the most common treatments there is (https://en.wikipedia.org/wiki/Blood_transfusion#Frequency_of...). Safety concerns seem to stem from so far unknown pathogens that are not tested for in the blood of donors.

3. Production facilities are every hospital. Nothing needs to be produced or what do you refer to?

I'm referring to my own clinical and scientific perception, which seems to be shared among my peers, but I didn't run a comparative study.

Right now, chloroquine is cheap. I suspect that will change. As for plasma yes, every step from collection to administration is expensive if you want to keep with the current safety level. And other people need plasma too...

Plasma toxicity worries currently comes more from transfusion-related reactions than from infection.

Hospitals have very limited capacity in term of production. Just starting with the fact that you'd have to find enough volunteers in the first place, but even so a hospital is not a factory.

Dr. Peter Attia did a few podcasts with a virologist discussing this.

It’s helpful in the short term, but not effective for longer than a few weeks apparently. Also there may be scaling issues?

Was it this one? https://www.globalhealthnow.org/2020-03/covid-19s-stop-gap-s...

> It’s not a vaccine. Think about it as the administration of a protein, it’s a liquid that is given to people that gives them immunity.

> Right. Because the vaccine would provoke the recipient’s antibodies. You'll have the antibodies, but they won't be your antibodies—though it'll do the same thing.

Yes. What do you want to say with the quotes from the article? Yes it is not a vaccine, neither are antiviral treatments.

The antiviral treatments undergoing trial are (for the most part) very inexpensive drugs that have been known for years or even decades so they don't need additional testing once they're proven to work and can be manufactured at scale almost immediately (since the production chains already exist).

This is only true of the chloroquines, and those are antiparasitics, not antivirals.

The difference of serum to vaccination is that any resistence/immunity gained from serum will only last until the antibodies are eliminated from your blood.

A vaccine triggers an active immune response. That includes the differentiation of aptly-called "memory" B cells. Those can lie dormant for decades and spring into action when needed.

The comparison here is not vaccine vs serum. It’s antiviral vs serum.