19 December

William Topley. In the 1930s one of the first researchers on the idea of herd immunity. The idea that if enough of us are immune to a disease, it will prevent it spreading at epidemic levels. This is why it pays to do the history when you’re doing the science. Because something Topley discovered hasn’t survived to discussions of herd immunity today. Herd immunity, he said, is achieved not just by people becoming ill or vaccinated, but also by organising your society in a way that prevents infections. Public health, we call it. Nobody needs to become infected at all, and the disease is defeated. Exactly how the world should approach Covid, and all infectious disease. We will always need to deal with infectious disease, and there won’t always be treatments or vaccines to save us.