In the November/December 2020 issue of Chain Store Age (https://issuu.com/ensembleiq/docs/csa_11_2020?fr=sZDA2MjgwODQ2MQ) there is an article by Marianne Wilson on Page 39 called, Breathing Easier: Addressing COVID with HVAC.
In the article, she discusses the success a large retail shopping center had with adding Needlepoint Bi-Polar Ionization to the existing HVAC systems to clean the air of both pollutants and airborne pathogens. It goes into good detail about how the system was chosen, how it works, and how quickly costs are recovered. They compared performance between areas with the NBPI system and those with it not yet installed.
It's one of the better responses I've seen to addressing healthier indoor environments without high cost or high maintenance.