> How long does the immunity last?

If we consider that recovered patients are immune between 6 and 8 months at least, that timeframe seems likely.

> What are the long term side effects?

I keep on asking myself. What vaccines do truly exhibit long term side effects? Narcolepsy with the 2009 swine flu vaccine or the Guillain-Barré syndrome for the 1976 flu vaccine do not fit the bill, because they actually showed up in the early months after administration (although some were found out later).