It is depressing that we have a health secretary who does not understand, let alone believe in, herd immunity (Tory rebels fire warning shot as 42 MPs vote against stricter Covid measures, 13 October). The three examples that he quotes of diseases that never reach herd immunity are all incorrect, in different ways.
With malaria, the problem is the lack of individual immunity, and with flu the problem is that different strains of the virus emerge from time to time, bypassing any herd immunity that has built up. But it’s his inclusion of measles that really upsets me. You do get herd immunity, in the adult population, but this gets diluted out because people keep having babies. This can be easily counteracted by vaccination of children.
Because measles is far more infectious than Covid-19, with R possibly as high as 20, achieving herd immunity requires vaccine uptake of about 95%. Obtaining that requires a continuing campaign to counter the ignorance and misinformation about vaccines that is circulating.
By wrongly suggesting that herd immunity is impossible for measles, Matt Hancock has just shot himself, and us, in the foot.
Prof Jeremy Dale
Glossop, Derbyshire
