[CaptainK]

If he had covid in December why would he need to get the shot 4 months later? What am I missing here?

[familyop]

There are many other articles out there to answer that question. This was one of the first few hits in a search.

Should people who’ve had Covid get vaccinated? Here’s what the experts say
https://www.cnbc.com/2021/02/05/should-you-get-vaccinated-if-you-recovered-from-covid-expert-advice.html

[familyop]

Little more info here.

Recovered COVID-19 patients may need only a single vaccine dose, suggests study
https://www.news-medical.net/news/20210416/Recovered-COVID-19-patients-may-need-only-a-single-vaccine-dose-suggests-study.aspx

[SisterK]

If he had covid in December why would he need to get the shot 4 months later?

He does not need the shot.
Four months later his antibody count should be very high.
For the rest of his life, his body will have memory of how to build antibodies to this virus.

But now he has jacked with his immune system so all bets are off.