Dr. Cillian De Gascun:

I can start and will then pass over to Professor Nolan. We looked at this in the EAG from an evidence perspective.

There is certainly very good evidence that medical grade face masks work very well in people who are symptomatic and in the healthcare setting. We gave that advice to NPHET a number of weeks ago. The challenge with masks in the community is that we believe that appropriate mask use is beneficial, but it is only as an add-on - an additional measure - to good hand hygiene, physical distancing, good respiratory etiquette and all that.

The challenge is that inappropriate mask use can be potentially harmful and can increase the risk of transmission. We know that the evidence on cloth masks and non-medical grade masks is not fantastic. People use the nice plausible hypothesis that because it stops the particles it is trapping the virus as well. We do not actually have great evidence in that area. As a barrier, it certainly prevents some particulate matter from spreading. Where people are symptomatic and coughing and sneezing, the mask will prevent onward transmission of particles that, we presume, contain virus.

However, many of the experiments that have been done to date have really been to demonstrate a proof of principle rather than actually demonstrating that virus is not transmitted. Obviously, based on the population-based studies from countries that have instigated universal mask usage from an early stage, I think it has worked. It is not the only measure that they have implemented so I think there certainly is a role for it and that is why our advice is that people in areas where they cannot physically distance should be wearing masks.