[Ken H]

Did he receive monoclonal antibodies? I read they are only given within the first 10 days of symptoms.

[bella1]

Has to be in the first 10 days to keep the virus from replicating before the cytokine storm kicks in.

[Paul R.]

Giving of monoclonals is not cut off by time, although 10 days is common. The real determining factor is blood oxygen level: Drop too low and the monoclonals are contraindicated because they'll likely then do more harm than good. With Delta, some people can drop to an O2 of 90 or below a few days after symptoms appear.

Also, if a complication is already developing / in progress, monoclonals and most prophylactic treatments are not likely going to treat it.