Starting July 4, 2021, and lasting past the holiday, members of the LGBTQ community converged on Provincetown, Massachusetts, for a holiday that was supposed to be a celebration of the end of the long COVID-19 lockdown. When the weather turned rainy, they confidently took the party indoors, packing the little seaside town’s restaurants, bars, and clubs. Why not? They were vaccinated and mask mandates had been lifted.

What happened next shocked both the revelers and the country, shutting down what had been hyped as a “hot vax summer,” and signaling that there was a long way to go before the pandemic was over. PhD student Lydia Krasilnikova—who co-led an 80-person, multi-organization collaboration examining the July 2021 superspreader event in Provincetown—talks about what happened and how the outbreak contributed to the US Center for Disease Control’s decision to resume its recommendation of indoor masking later that year.