Professor Philip Nolan:

The notion that one can have a negative PCR test today and a positive one after three days is not new to anybody. If I am exposed to the virus today it grows inside me undetected for three or four days. I could be exposed today, take a PCR test on Friday and be negative. Then the virus replicates very quickly so I could be PCR positive on Sunday or Monday. That is why, as the Chairman knows, quite frequently two tests are recommended because the virus can be latent.

It is interesting to propose that on top of that two test regime an additional rapid antigen test might pick up some cases that we are missing. It is not particularly plausible. It would mean that one would have to go from a position of having almost no virus or no virus detectable to having a very large viral load within 24 or 48 hours. In designing a pilot to check whether that would be a useful addition, one would have to be very careful about the number of people one includes. It might have to be very large study.

The fundamental point that we want to make is that as a country we need to prioritise. It is difficult to do a pilot study. We cannot have a scattergun approach, and decide to try something everywhere. It is important that we prioritise in what settings we will pilot the use of antigen testing. That will clearly be the settings where it will be a priori most likely to be useful. We then have to very carefully design the validation studies-----