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. The concept is that these people could safely return to work because they will have acquired immunity to the virus, so they won’t be at risk of developing COVID-19 again or reinfecting others. What the WHO was trying to say – correctly – is that while antibody testing has an important function in the response to the pandemic, immunity passports are a horrible idea. Yes, they were a major plot point in Contagion, but that was a movie. Reality doesn’t work that way.