"There is solid evidence emerging that COVID-19 patients are developing antibodies to the virus, as the human body does for most infectious pathogens." https://www.the-scientist.com/news-opinion/what-do-antibody-tests-for-sars-cov-2-tell-us-about-immunity--67425?utm_content=126688609&utm_medium=social&utm_source=twitter&hss_channel=tw-18198832

“What we’re seeing is that patients are [developing antibodies] anywhere from two to about fifteen days” after developing symptoms, Lynch says. In most patients, the antibody response is broadly reminiscent of the typical reaction to many other pathogens"

"The vast majority of patients developed antibodies that targeted the spike protein around 10 to 15 days after symptom onset, the scientists reported in preprint."

"In many viral infections, “the magnitude of an antibody response correlates well with how big the infection was,” Crotty notes. In other words, severe infections are more memorable to the immune system."

"Studies of survivors of the 2003 SARS epidemic suggest that concentrations of neutralizing antibodies lasted for up to three years. Although, a recent yet-to-be-peer-reviewed preprint reports to have found neutralizing antibodies in SARS survivors 17 years after the epidemic."

"Regardless of immunity, “with most diseases, if you get exposed to enough virus, you’re going to get sick”

[Same applies to vaccinated people by the way]

Given covid_19 is estimated to mutate 25 times in a year, we are looking at a 100 mutations before a world record breaking vaccine is ready, which means chances are it will not work on many of these mutations.

There is only one realistic medium term solution: herd immunity