USA Ultimate has just posted updated COVID-19 policies:

A summary of the notable changes for updates issued March 31, 2022 is as follows:

• Removal of pre-event proof of vaccination or negative PCR test for interstate events.
• Increased emphasis on state and local health regulations, and on personal responsibility around the use of risk-mitigating measures, including vaccination, testing and masking.
• Adjusted contact tracing and reporting protocols for participants and sanctioned event organizers, including:
  • Limiting the identification and exclusion of close contacts to events in progress.
  • Eliminating post-event tracking for close contacts.
  • Eliminating the need to submit a negative test prior to returning to play.