The news is full of stories concerning antibody responses to Covid 19. The reason is that along with “Memory T-cells”, IGG or “neutralizing antibodies” are essential for long-term immunity to the virus. If you receive a vaccine that requires booster shots, such as the measles vaccine, you are getting it because these long-term immune defenses are starting to weaken. We do not yet know how strong our long-term immunity is after infection to this particular virus. Until we do have a better understanding of this (which will require time) we cannot be sure that if or when people may be susceptible to reinfection. Here is a paper from Science that details this issue.
https://science.sciencemag.org/content/early/2020/04/24/science.abb5793.full