know that the vaccines now available across the world will protect their recipients from getting sick with Covid-19. But while each vaccine authorized for public use can prevent well over 50% of cases (in Pfizer-BioNTech and Moderna‘s case, more than 90%), what we don’t know is whether they’ll also curb transmission of the SARS-CoV-2 virus.That question is answerable, though—and understanding vaccines’ effect on transmission will help determine when things can go back to whatever our new normal looks like.The reason we don’t know if the vaccine can prevent transmission is twofold. One reason is practical. The first order of business for vaccines is preventing exposed individuals from getting sick, so that’s what the clinical trials for Covid-19 shots were designed to determine. We simply don’t have public health data to answer the question of transmission yet.The second reason is immunological. From a scientific perspective, there are a lot of complex questions about how the vaccine generates antibodies in the body that haven’t yet been studied. Scientists are still eager to explore these immunological rabbit holes, but it could take years to reach the bottom of them.