Sir

You may have been inadvertently off message about vaccination policy in your Editorial 'On message, off target' (Nature 452, 128; 2008) — for what you did not say. Centuries of experience have proved the importance of societies (not doctors, parents or vaccine recipients) in making decisions on whether to vaccinate or not. Having drafted the US national vaccine programme legislation that was passed in 1986, and directed the national vaccine programme in 1993–94, I can say that recent UK experience impressively illustrates the strategic distinction.

After an unexpected rise of pertussis (whooping cough) cases in the 1990s, Britain revamped its system to reward general practitioners for fully immunizing all children on their lists, paying a bonus to those who reached 90% then, a few years later, 95%. This system did not exclude from the denominator the small number of patients with good medical reasons against receiving vaccine.

Why the societal strategy? No vaccine is fully effective in everyone who receives it. Only 'herd immunity' can protect those in whom a vaccine does not stimulate protective immunity. Population health therefore improves where policies support full coverage of the population. Such policies create a culture in which health authorities educate doctors, parents and patients about the societal goals as well as individual contraindications.

Good immunization policies balance the risks of vaccines against the benefits. All vaccines, usually given to healthy people, pose some small risk. Good medical reasons do occasionally exist for some people to avoid some vaccines. Britain understood this, and designed its policy to avoid incentives for doctors to vaccinate in such situations. Although vaccination remains voluntary, no programme is based on individual preference. Public education about vaccination is important, particularly to heighten understanding of the basis for all aspects of public policy to maximize protection of human health.