The great immunisation debate

Ever since Edward Jenner first tried to vaccinate a young boy against smallpox in 1796, immunisation has been through multiple evolutions to become an effective barrier to a host of diseases, ranging from bacteria, viruses, parasites and cancers.

Vaccines consist of a weakened form of a disease. They stimulate your immune system to produce antibodies to fight the infection. So if you ever get the actual disease, the necessary antibodies are already present in your body and your immune system is ready to attack. This process is called immunisation.

All of the infections we are immunised against can develop into serious illnesses with the potential to cause disability or death. A wide range of vaccines have been produced to protect against conditions ranging from yellow fever and typhoid to meningitis and mumps. They are used on the principle that it is better to prevent people from becoming ill, than it is to treat them once they are ill.

Most vaccines are given to children. Routine vaccination against six key diseases - measles, polio, diphtheria, tetanus, pertussis (whooping cough) and tuberculosis is provided to children in most developed economies.

Some vaccines are given only to specific groups of people, for example the influenza (flu) vaccine. Influenza can lead to serious complications, and the vaccine is only given to people most at risk of these complications, including elderly people, those in nursing homes or with certain chronic medical conditions, pregnant women and healthcare workers( who are more likely to spread the virus to vulnerable people).

Other vaccines are offered if you are travelling abroad and may come into contact with diseases you would not find at home.

Why immunise?

Having a vaccine does not only protect you. If a large number of people are vaccinated against a disease, the spread of the infection in a community is significantly reduced, and even unvaccinated people are at much less risk of catching the illness. This is known as herd immunity. If enough people are immunised against a disease, it protects those who cannot be, such as very young babies and people with weakened immune systems.

As time passes, more and more people are being immunised. As this happens, the number of people who catch a disease every year will fall and eventually the disease should be eliminated completely. Vaccination has already led to the elimination of measles in the World Health Organisation classified region of the Americas, and polio has been eradicated in three of the WHO’s six regions. It is hoped that complete eradication of these two diseases will follow.

Because some diseases, such as polio, are now almost never seen in some developed countries, people have started to argue that there is no longer any need for children to be immunised. However, we cannot afford to become complacent. These diseases have not disappeared, and if more people choose not to have their children immunised, the number of people at risk of catching a disease will increase and outbreaks will occur.

The only time to stop immunisation is when a disease has been completely eradicated worldwide. For example, in 1979, it was certified that an immunisation campaign had completely eradicated the natural occurrence of smallpox in every country, so immunisation against the disease was stopped. Despite this, we still cannot be sure that it will not come back. The effects of the smallpox vaccine are thought to last for at least 10 years, but as immunisation was stopped in the 1970s, most people are now susceptible to the disease. There are fears of a terrorist attack using smallpox, which has led to the smallpox vaccine being stockpiled in case of an emergency.

Side-effects

As vaccines have become more widely used and disease incidence has fallen, people have also become more concerned about the potential side-effects of vaccines. In some cases, this has led to fewer children being immunised and disease incidence increasing.

The MMR vaccine (a combined vaccine to protect against measles, mumps and rubella) in particular has caused controversy. A study published in 1999 by a now discredited physician suggested a link between the MMR vaccine and autism. This theory was not proven, however, there was huge media coverage giving the impression that the link was certain. This led some parents whose children were born after 1999 to decide not to give them the vaccine, which in turn caused an increase in measles incidence in several countries, including the UK, Austria and Israel.

Another example occurred in Nigeria where, during 2002 and 2003, rumours spread that the oral polio vaccine was being used to lower the fertility of young girls. This led to the suspension of polio immunisation for a year in several parts of Nigeria, which in turn caused a nationwide polio epidemic that spread to 20 previously polio-free countries.

It is important to remember that for immunisation to carry on being successful, people need to continue being vaccinated, regardless of whether we see the disease where we live or not.

Looking to the future

Hopefully we have not seen the best of immunisation yet. There are an abundance of new vaccines in the research pipeline and some of these may be available as soon as 2012. Crucially, many of these vaccines are aiming to protect against diseases for which no vaccine currently exists, such as malaria and dengue fever. One malaria vaccine is currently in the later stages of clinical trials and if these go well, it could be licensed within the next few years.

Research is continuing into a vaccination for HIV, which infects around 14,000 people every day. Recently, an experimental vaccine has been shown to significantly reduce the risk of HIV infection. Although an HIV vaccine is still a long way off, advances such as this give us hope for the future, and perhaps even an answer within our lifetimes.

Therapeutic vaccination

Vaccines are usually administered to healthy people in order to prevent a disease. However, they can also be used to treat people who already have a disease – this is called therapeutic vaccination. Therapeutic vaccines stimulate your body to produce antibodies, which fight off disease.

A drug called glatiramer acetate is currently used as a therapeutic vaccine to reduce the frequency of relapses in people who have relapsing-remitting multiple sclerosis.

The research world has turned its attention to the field of therapeutic vaccines, particularly those that could treat cancer. Therapeutic cancer vaccines are designed to stimulate the immune system to recognise and attack cancer cells, thus delaying or preventing the growth of tumours.
Researchers often add substances called adjuvants to therapeutic vaccines. These substances boost immune responses and make the vaccines more effective. One problem in developing therapeutic vaccines has previously been a lack of adjuvants. However, scientists at Uppsala University in Sweden have recently discovered a substance that is considerably more effective than adjuvants that have been used in the past. This finding removes a major limitation in developing therapeutic vaccines and could mean that we are a big step closer to many more being produced.

A resounding success?

Immunisation is currently one of world’s most successful health interventions, second only to the provision of clean water. In future it may become more so if vaccines for conditions such as malaria and HIV can be produced.

The major failure of immunisation is in its lack of ubiquitous distribution. Children in many developing countries are dying from preventable diseases, simply because they do not have access to basic vaccines. Children miss out on vaccines because of a lack of government commitment and funding, remote and poorly equipped health services, because of war or natural disasters or simply because their families do not understand why they should be immunised.

The global health community has to find a way to give everyone equitable access to vaccines and therefore the right to protection against preventable diseases. Over recent years, more funding has been put into place. Governments and philanthropic organisations such as the Bill and Melinda Gates Foundation are now dedicating more money to vaccines and immunisation. Their donation is expected to save the lives of up to 34 million people, a staggering number which is testament to the power of what is perhaps humanity’s biggest health triumph – immunisation.