A few days ago, the World Health Organization caused a stir by saying that antibody tests may not indicate whether someone is immune from SARS-CoV-2. This led to some understandable confusion, and WHO spokespeople have subsequently walked the comments back a bit. While the messaging might’ve been handled better, the public health experts at the WHO were trying to make a very important point. Several prominent politicians have advanced the idea of issuing “immunity passports” to people who’ve recovered from SARS-CoV-2 infection.