Though well-known as a respiratory illness, COVID-19 can also affect the nervous system, bringing on headaches and fatigue and wiping out the sense of smell. But it’s unclear whether these symptoms are caused by an immune response or the virus itself invading the central nervous system (CNS). Now, researchers reporting in ACS Infectious Diseases have developed a new tool and possible vaccine candidate that could help scientists understand how SARS-CoV-2 could be invading these cells.