Vaccine: Encyclopedia II - Vaccine - Controversy surrounding the use of vaccines

Vaccine - Controversy surrounding the use of vaccines

See article: Vaccine controversy

Opposition to vaccination, from a wide array of vaccine critics, has existed since the earliest vaccination campaigns: [2].

A number of vaccines, including those given to very young children, have contained thimerosal, a preservative that metabolizes into ethylmercury. It has been used in some influenza, DTP (diphtheria, tetanus and pertussis) vaccine formulations. Since 1997, use of thimerosal has been gradually diminishing in western industrialized countries after recommendations by medical authorities, but trace amounts of thimerosal remain in many vaccines and in some vaccines, thimerosal has not yet been phased out despite recommendations. Some states in USA have accepted laws banning the use of thimerosal in childhood vaccines.

In the late 1990s, controversy over vaccines escalated in both the US and the United Kingdom when a study, published in the respected journal Lancet, by Dr. Andrew Wakefield suggested a possible link between bowel disorders, autism and MMR vaccine, and urged further research [3]. His report, which focused upon novel syndrome he described as autistic enterocolitis, garnered significant media attention, leading to a drop in the uptake of the MMR vaccine in the UK and some other countries. The study garnered criticism for its small sample size, and for failing to use healthy controls. In response to the controversies, a number of studies with larger sample sizes were conducted, and failed to confirm the findings.[4] [5]. In 2004, 10 of the 13 authors of the original Wakefield study retracted the paper's interpretation, without disputing the central finding of a consistent set of bowel disorders among the autistic study subjects, stating the data were insufficient to establish a causal link between MMR vaccine and autism.[6] In 2004 and 2005, England and Wales have seen an increase in the incidence of mumps infections among adolescents and young adults, which health authorities attribute to a decline in booster shots from 92% to 80%, which they believe is due to the alleged misinformation generated by Wakefield's study [7].

Also in 2004, the United States' Institute of Medicine reported that evidence "favors rejection" of any link between vaccines containing thimerosal, or MMR, and the development of autism [8].

Vaccine - Potential for adverse side effects in general

Some refuse to immunize themselves or their children, because they believe certain vaccines' adverse side effects outweigh their benefits. A variation of this reasoning is that not enough is known of the adverse effects to determine whether the potential benefits make the risks worthwhile. Since most people are vaccinated against contagious and potentially fatal diseases, the chances of someone who is not vaccinated becoming ill is a good deal smaller than it might be if their opinion was held by more people. Thus they acquire some of the benefits of vaccines, through herd immunity, without assuming the risks those who choose to vaccinate do.

Advocates of recommended routine vaccination argue that side effects of most approved vaccines are either far less serious than actually catching the disease, or are very rare, and argue that the calculus of risk/benefit ratio should be based on benefit to humanity rather than simply on the benefit to the immunized individual. The main risk of rubella, for example, is to the fetuses of pregnant women, but this risk can be effectively reduced by the immunization of children to prevent transmission to pregnant women.

Vaccine - Efficacy of vaccines

It's worthwhile to note that vaccines do not guarantee protection from a disease. That is, even having been vaccinated, there is still a remote possibility that a vaccinated person may get the disease. Adjuvants are typically used to boost immune response. The efficacy or performance of the vaccine is dependent on a number of factors:

• the disease itself (for some diseases vaccination performs better than for other diseases)
• the strain of vaccine (some vaccinations are for different strains of the disease) [9]
• whether one kept to the timetable for the vaccinations (see Vaccination schedule)
• some individuals are 'non-responders' to certain vaccines, meaning that they do not generate antibodies even after being vaccinated correctly
• other factors such as ethnicity or genetic predisposition (possibly)

In cases where a vaccinated individual does develop the disease vaccinated against, the disease will most likely be milder than if the individual had not been vaccinated.

Adapted from the Wikipedia article "Controversy surrounding the use of vaccines", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki