Click to zoom-in

A brief history of vaccines

As early as 1000 AD, there are reports of vaccination against smallpox in China. Dried smallpox scabs would be used to infect healthy people in the hope that they would develop a mild infection rather than succumbing to the often fatal disease (this method is called variolation). If this happened, then they would be immune to smallpox. There is evidence that this practice was widespread in Africa, India and the Ottoman (Turkish) Empire in the 17th century.

The modern methods of vaccine research and development began with a country doctor from Gloucestershire in England named Edward Jenner. Jenner observed that milkmaids who were infected with cowpox did not suffer from smallpox when there was an outbreak in the area.

In 1796 he performed one of the first clinical trials ever recorded; he took pus from a cowpox lesion on a milkmaid’s hand and infected an eight year old boy named James Phipps. Six weeks later, Jenner infected James with smallpox but he did not succumb to the disease. Jenner performed twelve similar experiments on sixteen other people (all poor farm labourers or inmates of workhouses) over a period of more than twenty years and published a scientific paper describing his results. His conclusion that cowpox infection protects people against smallpox is the foundation of today’s vaccinology.

Jenner became a celebrity in England due to his smallpox vaccine and received grants to fund further research from the British Parliament, in addition to many honours bestowed upon him by Oxford, Cambridge and Harvard Universities.

Popular interest in vaccines increased - by 1800 more than 100,000 people were vaccinated in Europe against smallpox, and vaccination was beginning in the USA after capturing the interest of President Thomas Jefferson. The vaccination programmes were funded by the ruling monarchies and governments.

The next major development in vaccinology came from a brilliant French chemist named Louis Pasteur. Pasteur produced a vaccine for chicken cholera by weakening the bacteria that cause the disease. He was studying cholera in chickens and accidentally left some of the bacteria in his laboratory during the holidays.

When the chickens were later injected with the bacteria they developed a milder form of the disease and survived. When Pasteur then injected the same chickens with more cholera bacteria they survived, thereby suggesting to Pasteur that the first injection with the older, weakened bacteria acted as a protective vaccine.

Pasteur then lent his attentions to developing a rabies vaccine. In 1885 a 9 year old boy was brought to Pasteur after being bitten by a rabid dog. Pasteur gave the boy a series of injections containing weakened rabies virus and he never developed the disease. Pasteur became well known for this success and many people came to him for treatment in the following years.

A revolution in modern vaccine production can be attributed to three scientists (Enders, Weller and Robbins) who successfully grew poliovirus in cells in a laboratory. They were awarded the Nobel Prize for their work in 1954, because their discovery enabled the large scale production of viruses that could then be inactivated and assembled into vaccines. This method is still used today.

To overcome the problem of introducing live bacteria or viruses into a person, scientists tried several methods of inactivating them. In the late 19th century, heat treatment was developed and vaccines containing killed bacteria were developed for typhoid fever, cholera and plague. Chemical treatments that made bacteria and viruses unable to replicate were developed in the mid-1900s.

A pioneer in this research, Dr. Jonas Salk, created an effective polio vaccine using chemical treatment to inactivate the poliovirus; the success of the vaccine gave Salk worldwide fame and laid the foundation for modern inactivated vaccines.

Public vaccination programmes spread worldwide when the World Health Organization (WHO) and United Nations Children’s Fund (UNICEF) were established immediately after the Second World War. The WHO’s first priorities were to reduce the transmission of tuberculosis, malaria and sexually transmitted infections, and to improve the health of mothers and babies.

The enormous impact of the WHO on public health can be demonstrated by their smallpox campaign in the 1960s and 1970s – smallpox was eradicated, with the last known case reported in 1977. When the campaign began, smallpox still killed one quarter of all people who contracted the disease.

Due to the WHO Expanded Program on Immunization (EPI), rates of childhood vaccination worldwide have increased dramatically, and child mortality rates due to communicable diseases have decreased. Due to vigorous vaccination programmes, deaths from measles worldwide dropped by 78% between 2000 and 2008, and life-threatening maternal and neonatal tetanus infections have been eliminated in 20 of the 58 high risk countries.

The next disease expected to be eradicated is polio – polio infections are still reported in a handful of countries due to insufficient vaccination rates, but the efforts of health organisations are slowly eliminating these.

Since the introduction of vaccines, there have been critics who are concerned about their safety. In recent years there has been much-publicised concern by some parents about an alleged link between the rise in autism diagnoses and the preservative thimerosal (previously used in diphtheria, tetanus, pertussis, Hib and Hepatitis B vaccines).

A series of comprehensive studies have demonstrated that thimoserol does not cause autism, but to counter any fears, thimoserol has been removed from most vaccines.

Similar suspicions of a link between autism and MMR, arising from incorrect claims by an English doctor in the 1990s have remained in public opinion, despite numerous studies proving that the original claims were incorrect. These suspicions have resulted in reduced vaccination rates of children in some regions, and the rise in life-threatening infections such as measles.