We’ve been in the midst of a pandemic for over half a year now. We already know that masks provide short-term protection and, eventually, a vaccine will provide long-term protection.

Current estimates say roughly 40% of individuals with COVID-19 are asymptomatic (i.e., will never develop symptoms) and all other COVID-19 patients are presymptomatic (i.e., have not yet developed symptoms) for 2-14 days. The uppermost estimate from seroprevalence studies indicate up to 10× as many people infected, likely without severe symptoms. This means most people spreading SARS-CoV-2 probably aren’t even aware that they are contagious, making masks essential for reducing viral spread.

Facial coverings– from a well-fitting N95 mask, to a triple layer cloth mask, to a thinly stretched single-layer neck-gaiter– provide varying degrees of protection. The better the face covering, the better it protects both the wearer and the people around them. Ideally, we’d all be able to wear nice-fitting N95 masks, although washable triple-layer cloth masks are a thrifty alternative without the trash and litter we see from many disposable surgical masks.

Recent estimates for herd immunity state that a minimum of 50-70% of a population needs to be protected against COVID-19. The highest estimate from the WHO and some recent studies put the number of infected persons around 10% so far. Some diseases, e.g., measles or pertussis, require over 90-95% vaccination rates to prevent outbreaks. No vaccine is perfect and some persons are unable to receive vaccines, unable to develop a long-term response, or lack a sense of social responsibility, so we’ll never see an effective 100% immunization. Even though some outbreaks may occur in areas with lower vaccination rates, this overall rate can prevent or end a pandemic.

These are very rough estimates but, if masks are, on average, 50% effective, then 100% usage would be equivalent to a 50% immunization rate of a population. Because some masks are more effective (e.g., N95) and some are much less effective (e.g., neck gaiters), every person needs to be wearing facial coverings of a high enough quality to reach an average of at least 50% effectiveness. Short-term, this would make masks as effective as a vaccine will be in the long-term. It’s a rough approximation, but the idea is pretty simple and easy to grasp.

There is no question that universal masking would end the pandemic while we wait for a long-term alternative; the only question is whether enough people will wear masks and then choose to be vaccinated. To be fair, that’s not the only way out; we could just wait for at least 0.5% of the world’s population to die off instead (~40 million people).