There are several coronaviruses that cause what's commonly known as "the cold". If you catch one and recover you're likely to be immune against infections from

There are several coronaviruses that cause what's commonly known as "the cold". If you catch one and recover you're likely to be immune against infections from the same viral strain for some time. For SARS-CoV2 and the COVID-19 disease it causes this means that even without the - quite likely - availability of a vaccine over time natural immunity will build up within individuals and the population as a whole, which has the potential of both making the resulting disease less severe and future waves spreading less. If most individuals who contract the virus during the next few months can't get sick anymore and can't spread the virus anymore for the about 6 months those individuals are taken out of the equation, which leaves less individuals for the virus to spread to in the next wave.