Wearing a face mask is certainly not an iron-clad guarantee that you won’t get sick—viruses can also transmit through the eyes, and tiny viral particles, known as aerosols, can penetrate masks. However, masks effectively capture droplets, which is the main transmission route of coronavirus. Some studies have estimated a roughly fivefold protection versus no barrier alone (although others have found lower effectiveness levels).
If you are likely to be in close contact with someone infected, a mask cuts the chance of the disease being passed on. If you’re showing coronavirus symptoms, or have been diagnosed, wearing a mask can also protect others. So, masks are crucial for the health and social care workers looking after patients and are also recommended for family members who need to care for someone who is ill—ideally, both the patient and caregiver should have a mask.