No. The original study will continue unaffected – we’ll still recruit 20,000 participants with non-Covid-related ME/CFS.

Recruiting the extra participants will benefit the original study, whichever way the results turn out.

If we find DNA differences between people with post-Covid ME/CFS and other people with ME/CFS, that will help researchers to understand what causes ME/CFS following Covid. And if those people had been included in the original 20,000, they would have diluted the results, making it harder to get clear findings.

However, there may not be any differences between people with post-Covid ME/CFS and others. And in that case, we’d have a larger study, with up to 25,000 people in it instead of 20,000. This larger study will have more power to identify causes of ME/CFS.

You can find more about this part of the study here.