Health professionals do not understand mathematical models

doi:10.1136/bmj.320.7234.581/a

BMJ 2000;320:581 ( 26 February )

Letters

Health professionals do not understand mathematical models

The first 150 words of the full text of this article appear below.

EDITOR $---$ The science commentary on herd immunity that accompanied the article by Panagiotopoulos et al on an increase in theoccurrence of congenital rubella after immunisation seemed irrelevant.¹In this letter we attempt to explain the relevantissues.

Immunising a proportion of the population reduces the risk of infection (not necessarily disease) among those who are notimmunised. This indirect protection from infection is termed herdimmunity. It can be manifested in two differentways.

Firstly, if the level of vaccine coverage is high enough (the proportion of those who are susceptible is low enough) thentransmission cannot be sustained, leading to elimination of theinfection from the population. This threshold of coverage (occasionallytermed the herd immunity threshold) is what Berger was attemptingto explain in hercommentary.

Secondly, if coverage is below the threshold then the infection will remain endemic. Individuals who have not been immunisedwill . . . [Full text of this article]

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Relevant Article

Increase in congenital rubella occurrence after immunisation in Greece: retrospective survey and systematic review • How does herd immunity work?: Takis Panagiotopoulos, Ioanna Antoniadou, Eleni Valassi-Adam, and Abi Berger
BMJ 1999 319: 1462-1467. [Abstract] [Full Text] [PDF]

Rapid Responses:

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But the teaching has to be right!: G H Hall
bmj.com, 25 Feb 2000 [Full text]
Re: But the teaching has to be right!: B. Burt Gerstman
bmj.com, 17 Jul 2002 [Full text]