[nudephil (OP)]

Paul asks:

With reference to Covid-19, isn't using the blood plasma of someone who has survived this virus a good way of building a primary antiviral solution?

Can anyone answer?

[set fair]

building a primary antiviral solution is goobledeegook.

If you mean could serum containing antibodies taken from a recovered patient be used to treat covid-19. You would need to read up on why such treatments have fallen out of fasion. I expect part of the reason is that such treatments do not readily lend themselves to the overesteemed double blind test. The treatment has been used in China, but I haven't heard them recommend it. I don't know the reasons but it may leave treated patients without immunity so that they can get reinfected or it might damp down the virus only for a limited time.

[Colin2B]

What is often called "convalescent plasma" has been used on a daily basis in the health service to help combat other viruses, as well as internationally in response to Sars1 and Ebola epidemics. It is being used in a trial against Covid19 at University Hospital of Wales in Cardiff.
This isn’t used as a vaccine, but to assist a patient fighting the disease.