One of the key things about science – obvious to its practitioners, but often obscure to outsiders – is that it is fuelled by doubt, not certainty. When the ‘facts’ change (as they often do), and when original assumptions are qualified or overturned, then any scientist worth their salt re-examines and, if necessary, alters their conclusions. The presence of cross-reactive helper cells in maybe half the population means that ideas about a possible second wave must be rewritten. This finding must make a second wave less likely, probably much less likely. And the fact that there has been no ‘second wave’ (as opposed to isolated outbreaks) anywhere where lockdown has been released also fits this hypothesis. It may well also explain why the first wave didn’t infect much higher proportions of the population.