Keeping fresh, filtered air circulating in a building is only one element of a comprehensive strategy to limit the spread of COVID-19, but like the others (including but not limited to keeping surfaces clean, social distancing, reducing building occupancy where practical, masking, and of course vaccination) it can be an important contributor to lowering the amount of spread, even if it, like the others, is not a single magic bullet.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is the best source for information on designing and maintaining HVAC systems, and has put together a lot of resources related to COVID and indoor air. Those resources are collected here, and we would particularly note their recommendation on upgrading and improving filtration that, “mechanical filter efficiency be at least MERV 13 and preferable MERV 14 or better to help mitigate the transmission of infectious aerosols.” ASHRAE notes, however, that higher filtration efficiency carries a “penalty” of requiring higher air pressures to drive or force air through the filter, which may be a particular problem in systems which were designed for lower filtration efficiencies. And while increasing air changes per hour (ACH) is likely desirable as a means of discouraging COVID spread, more efficient filtration makes it more difficult and expensive. Reducing air leakage from HVAC systems, such as with the Aeroseal® process, can help to mitigate that tradeoff.
The U.S. Environmental Protection Agency (EPA) also has a summary of Science and Technical Resources related to Indoor Air and Coronavirus.
In addition to Aeroseal, Airways distributes MERV-13 rated filters and other high efficiency filters which can be another important part of your COVID mitigation strategy.
Stay healthy and safe!