. With the visible disappearance of many vaccine-preventable diseases and the rise of "New Age" philosophies combined with the power of the media, the views of the anti-vaccination lobby appear to be gaining in influence. There is now a real concern that they could seriously threaten the remarkable gains made in controlling and eliminating many of the scourges which have beset mankind.

Vaccines represent one of the most successful and effective interventions in medicine. A dramatic example is smallpox, which was responsible for some of the most formidable epidemics of humankind. In 1967 it was the cause of 2-million deaths; a decade later it was totally eradicated from the planet by a concerted global vaccination programme. This and other dramatic successes of vaccinations are still being attributed by anti-vaccination groups to improved hygiene, sanitation, nutrition and living standards. This is simply not so.

Universal vaccination against Haemophilus influenzae, Hib, (a major cause of meningitis and pneumonia in infants) was introduced only in 1990 in the United States when living standards were hardly different to the present and this rapidly resulted in a precipitous drop in the number of cases and is now close to being eliminated in that country.

Where anti-vaccination sentiments have unfortunately influenced public opinion the result has been immediate and dramatic. For example, in the UK a drop in vaccination against whooping cough in 1974 was followed by an epidemic of over 100 000 cases and 36 deaths in 1978.

Outbreaks of vaccine-preventable diseases occur periodically in communities refusing vaccination on religious grounds. Among members of the Dutch Orthodox Reformed church (about 2% of the population of the Netherlands), two outbreaks of paralytic poliomyelitis occurred in 1978 (110 cases) and in 1992 (71 cases) and measles in 1999-2000 (2 961 cases, 3 deaths).

There are some 30 dedicated anti-vaccination sites on the web and an additional 300 sites also lobby against vaccination. What moves the anti-vaccination groups? Broadly speaking, objections to vaccines can be grouped into three categories. Firstly, general fears about safety; secondly, misconceptions and myths; and thirdly, philosophical and religious objections.

Safety is an issue in the development and manufacture of vaccines, because vaccines are generally administered to healthy people, mainly children, to protect against diseases which the recipient may only potentially be exposed to.

Globally, safety standards for vaccines are extraordinary high and in South Africa, as elsewhere in the world, any possible side-effects are monitored, recorded and investigated by a system known as VAERS (vaccine adverse events reporting system).

The second category of vaccine objection is based on myths and misconceptions which surface from time to time and are repeatedly used by anti-vaccinationists to "substantiate" the hazards or the irrelevance of vaccines. An example is the supposed association between the MMR (measles, mumps and rubella) vaccine and autism and chronic bowel disease. In nearly all cases they are products of the logical fallacy of post-ergo propter hoc ("after this, therefore because of this") which mistakes association for causation. However, despite the overwhelming scientific evidence to the contrary, objections to vaccination persist.

With some parents there may be an intuitive perception that injecting a foreign material into a child is a cruel and unloving act. The refusal of vaccination is often born from a New Age value system which supersedes rational analysis and reasoning. More basic are those objectors which fall into the "free-loading" category "as long as everyone else gets the vaccine there is no reason my child should get it". In an industrialised country such as the US, those choosing exemption from statutorily compulsory vaccination were 35 times more likely to contract measles than vaccinated persons
In response to what is often seen as scientific arrogance and sometimes called "scientific terrorism", New Age and Mother Earth thinking and related alternative health practices have flourished under the guise of promoting "informed choice".

Parents want the best for their children. Unfortunately a worryingly strong message is going out to parents to "play-it-safe" and avoid vaccination. On the other hand for a parent nothing could be more heart-rending than seeing a child severely damaged by a disease which could so easily have been prevented by a simple vaccine.

nThe Star's Contributing Editor Professor Barry D Schoub is executive director of the National Institute for Communicable Diseases. A bibliography of the relevant scientific literature can be found on the National Institute for Communicable Diseases' website http://www.niv.ac.za