An Instagram post asks “If masks work, then why are you bothered about people who don’t have one on, your masks work right?”. The post seems to suggest masks are only effective for the wearer.
While facemasks are considered to offer some personal protection to the wearer from Covid-19 (and some, such as respirators are thought to offer a fair bit of protection this way), a really important part of the way that facemasks and coverings can reduce the spread of Covid-19 is through ‘source control’.
This is where a facemask or covering reduces the number of particles released into the surrounding air by an infected wearer. In this capacity, wearing a facemask offers protection to others rather than just to the wearer. This is particularly important in preventing people from spreading Covid-19 before they know they are infected, for example before people have symptoms, or if they have the infection asymptomatically.
There are lots of different types of facemasks and coverings, and other factors such as the fit, the number of layers of material they include and the environment also make a difference to how well a mask can offer protection to the wearer, or to others.
A 2020 article in Nature reported that animal studies and observational studies in humans add to evidence showing a correlation between mask wearing and a reduction in the spread of the virus from an infected source.
The World Health Organisation advises that, in addition to other actions, “masks are a key measure to suppress transmission and save lives”.
The latest guidance on when you are legally required to wear a facemask can be found on the government website.