Professor Martin Cormican:

On the airport side, in particular, you are looking at essentially filtering the flow of people. PCR is the best available filter we have. Antigen testing, we can see from the evidence, will filter out fewer people who are carrying the virus than PCR will. You can make a policy decision - some countries may have made a policy decision - to use the filter which has bigger pore sizes and some countries may use the smaller ones, but that is a policy decision. What we need to be very clear on is that the pore size in the PCR filter is smaller and it is a better filter and the pore size in the antigen test is a bigger pore size and it is a less effective filter. You can choose which filter you want but it is important from a scientific point of view to be clear on what you are choosing, what the differences are and how effective each of those two filters are if you choose to use them. Right now, we do not have the evidence about how effective that filter with the bigger pore size is.