Rep. Raúl Grijalva, D-Ariz., (left) speaks before the start of a House Natural Resources Committee in June. Grijalva recently tested positive for the coronavirus. Bill Clark/Pool/AFP via Getty Images hide caption toggle caption Bill Clark/Pool/AFP…

Potential COVID-19 vaccines are kept in a tray at Novavax labs in Maryland on March 20. The Novavax vaccine requires an immune-boosting ingredient called an adjuvant to be effective. Andrew Caballero-Reynolds/AFP via Getty Images hide…