$SRNE vumc.org/viiii/spotlight/an... So, what’s the difference? And why do we need both? While an antibody can immediately treat an existing SARS-CoV-2 infection, a vaccine will train the immune system to battle future infections. We must develop a vaccine in order to afford the general population immunity to SARS-CoV-2, but must also have an antibody therapeutic to treat those who are already infected, or persons who have a medical condition that precludes them from being vaccinated (such as an immune deficiency). Having both of these powerful tools in our arsenal will ensure that the majority of the population is protected from the severe effects of COVID-19.