The German virologist Drosten said in an interview (a while ago, sorry, no source) that it is expected that survivors will stop producing white blood cells at some point. The next time they get infected with COVID-19 they will develop symptoms of a common cold and get rid of the virus much quicker.
Our immune systems have an inane immune system, an adaptive immune system, a Complement Protein system[0], with hundreds of thousands of proteins that have evolved over millions of years to change shape and form to grab onto and destroy all kinds of bacteria and viruses in the most random/crazy ways possible (It's a lot like microservices, except random monkeys throwing code at a wall and eventually making things work over millions of years), and many many other pieces.
Every vaccine we have today is either based off an inactivated virus or an attenuated virus (a virus moved though hosts to be less lethal to humans). The first vaccine used HorsePox/CowPox to create immune memory for SmallPox by Jenner, 185 years ago.
A lot of these newer vaccines like mNRA vaccines, are not vaccines at all. They attempt to generate antibodies specifically. But there could be hundreds of other interactions that occur when a virus enters your system, that can help build immunity. There's a lot we simply do not know about.
Attempts at SARS1/MERS vaccines led to Imunopathic responses and Immune Enhancement Syndrome. Vaccines are some carefully engineered, invention of science. They came about due to horrific diseases, where doctors tested and experimented on human beings because thousands were going blind, getting paralyzed or dying.
The rush to create a vaccine, with methods that have never successfully created a vaccine before, should be of great concern to everyone.
Is there even enough evidence in those few cases that it was really a reinfection? RT-PCR based tests are good but are not perfect after all, false positives happen.
If you run a RT-PCT enough times, you can generate a match in many cases where someone has never had the virus. The inventor of the PCR (who passed away years ago) took great issue with the way PCR was being using incorrectly with HIV testing. Even today with HIV, PCR is often reported with a viral load number, so doctors can tell what amount of antiviral drugs are needed for patients, and to help identify long-term non-progressives (rare) who may not need drugs at all.