That's not exactly new information. It's why hospitals are always so stiflingly hot, recovery rate goes up with temperature to a point much higher than 18C. Amongst the general (non sick or frail) population it does rather depend on clothing worn and activity level. People who work outdoors in the UK spend most of their lives below 18C without incident, mostly because they wear sufficient clothing. With declining activity and temperatures significantly below that it does get difficult, some of the butchery factories where I've worked run at 8-10 deg C with only moderate activity levels, it's very difficult to wear enough clothes to stay warm. This was evident during Covid, chilled food factories became reservoirs of infection and elevated transmission rates for a variety of reasons related to the indoor temperature.