ASHRAE has  page of downloadable position papers and recommendations for dealing with Covid 19 in HVAC systems and buildings. They updated their Building Readiness guide recommendations in January 2021 for reopening buildings. Some of the key points are

• Flush buildings before and after occupied periods with at least 3 air changes of fresh air.
• Use minimum MERV 13 filters. Higher MERV filters are preferred if your system can handle them
• Introduce outdoor air ventilation continuously during occupied times, even if a small number of people are in the building.
• Fan operation and ventilation are desirable, however, avoid airflow patterns that set up strong air currents.
• Limit re-entry of contaminated air. For example, make sure your “fresh air” is not actually recirculated from inside exhaust air or pulled from an area where people congregate outside.

ASHRAE Covid Resources page can be found here

https://www.ashrae.org/technical-resources/resources

The complete ASHRAE Position paper can be downloaded here