COVID-19 is a new disease. We are still learning how long both vaccine immunity and natural immunity (from actually catching COVID) last. There could be variations in immune responses from person to person because of age, medical conditions, medications they may be taking, or other factors. It’s important to know that immunity from the mRNA vaccines is stronger and more reliable than natural immunity.
Medical experts continue to study both vaccine and natural immunity closely so we can better fight COVID as a community.
SOURCE: https://www.yalemedicine.org/news/covid-19-vaccine-comparison (Yale Medicine)