The study found IgG levels and neutralizing antibodies started to decrease within two-three months after infection with novel coronavirus. The reduction was more (40%) in the case asymptomatic individuals than symptomatic individuals (nearly 13%). A few countries, including UK, were toying with the idea of issuing some form of a certificate to people who have […]
via Antibodies against coronavirus start to decrease in 2-3 months, study finds — Science Chronicle
lifeunderwriter.net 
So, after those three months can we be reinfected, or will the phenomenon of recrudescence take place?
The best answer at this point is we don’t know. But if look at the spectrum of infectious diseases the answer is probably yes.
So I’m wondering what will this mean regarding a vaccine? Will it be like influenza, and a vaccine one has to get annually? Or will it be more like HIV, without a vaccine ever?
A vaccine is preferable, like your annual flu shot. But the more we learn about this virus we may end up with drugs along the lines of the anti-virals similar to the ones used for Hepatitis C and HIV. Just my non-medical opinion.
It’s going to be interesting to watch it play out. I so hope they will be able to develop a vaccine. I agree that would be preferable. But it may end up like you said being some thing where some infected people need to take chronic antivirals.