MRC National Institute for Medical Research, London

Is vaccination really necessary? by Xi-lin Wu of Henrietta Barnett School]

Some people think the risks of vaccination exceed the risks from the diseases we want to suppress

One of medicine's greatest triumphs, the development of vaccination, has been and still is a crucial weapon in the battle against infectious diseases. However, fuelled by high profile cases in the media, scepticism is growing as people begin to weigh up the benefits of vaccination against the risks. So what exactly is vaccination and what are the benefits?

When pathogens such as viruses or bacteria enter our body, their protein or polysaccharide coat (the antigen) causes lymphocytes in the body to produce antibodies which combine with the antigens to neutralise their action. Phagocytes (also attracted to the antigens) migrate to the site of infection and engulf the pathogens, thus destroying them. The body now recognises these antigens and if infected again with the same pathogens, its immune response is much faster; antibodies can be produced before the full symptoms of the infection develop. However, antibodies are specific and cannot recognise antigens that have never invaded before; thus there is a time delay in producing new antibodies to counteract new antigens. During this period of time delay, the patient may experience the full symptoms of the infection, which could prove fatal. Vaccinations therefore are often used to stimulate an antibody response to certain dangerous micro-organisms. This can be done through active immunisation, where the body is encouraged to produce its own antibodies or, in certain emergency circumstances, when the body's own antibodies cannot be produced in time, 'ready-made' antibodies obtained from another organism are used instead as a form of passive immunisation. Although relatively short-lived, passive immunisation is an effective way of preventing irreversible damage that may be caused by the infection and usually helps to promote recovery (Parish, 1968).

For hundreds of years vaccination has helped save countless lives. While the first 'modern vaccine' was developed in the late eighteenth century, people were benefiting from protective inoculation as far back as 590AD when the Chinese first recorded their method of immunisation against smallpox: using a tube to blow dried scabs from smallpox pustules into the nose (Parish, 1968). Although not entirely successful, this did provide some positive results and inoculation against various diseases continued in similar forms until 1796, when Edward Jenner made his groundbreaking experiment with human-to- human vaccination. At the time rumour had it that cowpox (smallpox in cows) could provide protection for humans against the human form of smallpox. To test this theory, Jenner boldly inoculated a healthy eight-year-old boy with materials from a cowpox sore found on a milkmaid's hand. A sore developed at the site of inoculation but the boy remained healthy. To actually prove cowpox provided protection against smallpox, Jenner then injected the smallpox virus into the boy six weeks and several months later; the virus had no effect on the boy (Razzell, 1977)! This marked the beginning of vaccination which was further developed by Louis Pasteur. Through a lucky accident, he found that anthrax cultures kept at 42-43°C (instead of 37°C) for more than one week reduced dramatically in virulence. This led to his discovery that attenuation in virulence is directly linked to length of time the culture is left to grow, leading to his development of the anthrax vaccine (Parish, 1968).

Since Jenner and Pasteur, many scientists have worked on creating new vaccines and improving their effectiveness. Thanks to them, smallpox (the most infectious disease in Europe during the 18th century) has now been totally eradicated while the full symptoms of rabies can be prevented by passive immunisation. Although we have not yet repeated this success with any other diseases, vaccination has definitely helped contain the spread of diseases such as tetanus, tuberculosis and whooping cough. The World Health Organization also hopes polio will be eradicated by 2005 (http//news.bbc.co.uk); so with such significantly positive progress in the development of vaccination, what is the problem?

One of the main problems with vaccination, as with most medical treatment, is the possibility of side effects. The benefits of vaccination to individuals and the public as a whole need to be weighed against the side effects sometimes experienced by certain individuals. Such weighing of risks and benefits is proving exceptionally difficult for many parents following the controversial link between the triple jab for measles, mumps and rubella (MMR) and autism. One report (Wakefield et al., 1998) published in a medical journal (The Lancet) led to a nationwide debate on whether the benefit of the triple jab is sufficient to outweigh the possible risks of a child developing autism after having the jab. Although only a small sample of children was used for the research and no other research has backed up the claim, it immediately resulted in a reduced number of children being immunised. While the worry was over mixing the vaccines and combining the various antigens in one jab to reduce the number of injections given, this led to a common misconception that vaccines in general are potentially unsafe and resulted in a sharp fall in the number of children being vaccinated against MMR. Since then, The Lancet has itself criticised the paper's claims, following revelation of 'a conflict of interest' on the part of the author. Despite this, public confidence has yet to be regained, as many still question the benefits of MMR. In a similar case in 1974, the whooping cough vaccine was linked to brain damage and convulsions (Matthews, 1998). Vaccination rates fell to 31% as parents sacrificed public health and welfare for the personal well being of their child. This led to the worst outbreak of the disease for 20 years, before further investigation failed to reveal any relationship between the two. While both incidents highlight public scepticism towards the risks of vaccination, they also show the devastating effects of a decrease in vaccination rates (let alone no vaccination at all).

So far, vaccination has helped prevent infectious disease but there is now hope vaccination can be used to treat disease. In fact, one in six of all new cancer treatments being developed is a vaccine, designed to use the body's own immune system to eliminate cancer. Normally cancer cells are not recognisable by the immune system as tumours are not considered 'foreign'. However, there is now hope that vaccination can be used to make the cancer cells detectable to lymphocytes, by taking cells from the tumour and modifying them to alert and 'kick-start' the immune system. Positive results were shown in a trial for kidney cancer: 77% of those given a vaccine are still alive five years after their operation compared to the control group (who were not given the vaccine), where only 68% are still alive after five years. Even more positive was the fact that the vaccine produced only a few side-effects compared to conventional methods of treatment (Hawkes, 2004). Although there is still a long way to go before vaccination becomes a fully effective method for treating cancer, this certainly shows the potential benefits of vaccination for the future.

Overall, while the risks linked to vaccination need to be recognised, we cannot fail to acknowledge the close negative correlation between vaccination rates and incidence of infectious disease outbreaks, as shown by the whooping cough situation. Vaccination has undeniably helped to significantly reduce infection and transmission of diseases. This is beneficial not only on a personal level but to society as a whole. The hope that vaccination can, some time in the future, help cure deadly diseases, such as cancer, is a new and exciting prospect. We must constantly monitor the risks of vaccination and for those individuals who are suffering as a result of vaccination, maybe society as a whole should offer them more support rather than condemn the principles of vaccination. We cannot neglect the fact that vaccination has helped save millions of lives and continues to do so. Surely we should not reject vaccination due to the risks but strive to find ways to reduce these risks.

References

• Hawkes, N. The Times, Feb. 21; 2004
• http://news.bbc.co.uk/go/pr/fr/-/1/hi/health/3564891.stm
• Matthews, R. Biological Sciences Review 11(3):20; 1998
• Parish H.J. Victory with Vaccines - E & S Livingstone Ltd. 1968
• Razzell, P. The Conquest of Smallpox - Caliban Books. 1977
• Wakefield, A.J. et al. Lancet 341:637; 1998
• www.timesonline.co.uk