During the pandemic, we learned that face masks are a highly effective tool for reducing the transmission of COVID-19 because they help contain the spread of respiratory droplets, the primary means of infection. Although we still havent reached herd immunity, scientists are already thinking ahead to how face mask usage might prove beneficial after the pandemic. HuffPost spoke with experts who explained how and when masking up might be appropriate, even after the threat of COVID-19 has subsided.During flu season, if youre sick Proper mask compliance did more than protect against coronavirus: Last year, we saw the lowest number of flu infections in recorded history. Like COVID-19, influenza is a respiratory virus that is spread by inhaling infected droplets. Many coronavirus public health guidelines would also apply to influenza: wash your hands, stay home if youre feeling sick and wear a mask if you cant safely distance from others indoors.Masking is always good in terms of protecting people from respiratory diseases: If youre the infected person, youre less likely to pass the infection to someone else, said Bernard Camins, medical director of infection prevention at the Mount Sinai Health System. Camins noted that our standard, pre-pandemic cover your cough public health messaging might not go far enough. Instead, guidance going forward should include telling people to stay home if theyre sick and to wear a mask if theyre experiencing symptoms and arent able to stay home.When you want protection in crowded, indoor spacesWe have learned that close contact with others in poorly ventilated spaces is the fastest way to spread the virus. Even after COVID-19, well be putting ourselves at risk of contracting respiratory infections from the flu to the common cold whenever we find ourselves in crowded indoor spaces.It could make sense to mask up in some of these circumstances for extra protection, said Fred Pelzman, general internist and associate professor of medicine at Weill Cornell Medicine.When youre around a lot of people you dont know in a situation with contained air thats not recirculated, I think masks will continue to be important, Pelzman told HuffPost, naming packed movie theaters, school auditoriums, indoor sports arenas and public transit as examples of spaces in which distancing can be difficult. As technology improves and we learn more, we might see improvements to indoor ventilation systems and protective measures that could make indoor spaces safer overall. Right now, schools, stadiums, and bars and restaurants have used temperature checks and/or rapid testing to screen people who want to go inside. Both methods have limits to their accuracy, but over time we could see modifications that lead to greater efficacy, Pelzman said. Wearing a mask can offer protection against respiratory illnesses when you're in close proximity to others.When there are new variants of COVID-19 or when your immunity is lowerCOVID-19 will likely never fully go away. Even if we reach herd immunity which gives us strong protection from the virus it will continue to exist in the population. And, much like the flu, it will continue to mutate, with new variants emerging. Data shows that vaccines provide robust immunity for at least six months, but its still unclear how long protection remains after that. Scientists are working on Pfizer and Moderna booster shots, and they say we could need them within 12 months of first being vaccinated. Because there are still examples of vaccine breakthroughs cases in which vaccinated people contract the virus and due to vaccine hesitancy, there are still vulnerable people, the virus might continue to spread and evolve with new variants, Camins said. Faced with these unknown risks, universal masking could help protect us from spreading the virus as new variants emerge until we get booster shots.During travel or when around at-risk populationsVaccination rates and cases of COVID-19 infections currently vary widely between U.S. regions and between countries. Until we reach herd immunity worldwide the timeline for which is still very much a question mark were potentially exposing vulnerable populations who arent yet vaccinated when we travel from low- to high-risk areas. Wearing masks on airplanes or other modes of transit, as well as in public spaces if were among an at-risk population, can help keep everyone safe.Its key that public health officials continue to track and monitor communities to know the prevalence of the virus, Pelzman said. And before you travel, look up the COVID positivity rates and vaccination percentages for your destination. The coronavirus is not the first new virus outbreak and it probably wont be the last. But we do know that wearing masks when we cant safely distance from others can help protect us from contracting and spreading infection. Continuing that habit of masking up in certain situations could help manage the risk of widespread illness down the line.