martes, 4 de diciembre de 2018

Vaccine History

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By Ananya Mandal, MDReviewed by April Cashin-Garbutt, MA (Cantab)

Vaccines have been found to be the most successful and cost effective public health measures that prevent disease and save lives. This is particularly true among children all over the world. Over the last half of the 20th century, diseases that were once all too common became rare in the developed world, due primarily to widespread immunization. Hundreds of millions of lives have been saved and billions of dollars in public health expenditures have been saved with widespread vaccinations.

Smallpox

In the 20th century alone, smallpox was responsible for an estimated 300 to 500 million deaths. In 1967, the World Health Organization (WHO) estimated that 15 million people contracted the disease and 2 million died that year. Since the 1970’s and 80’s small pox is completely eradicated from all parts of the world through the effective use of vaccines.

Polio

Polio is a severely debilitating illness that may leave a child paralyzed for life. In the years following World War II, polio was the most feared disease among parents in the United States.

In 1952, polio permanently paralyzed 21,000 people in the United States alone. With the development of vaccines against polio, the rates have gone down by more than 99 percent.

The fight to fully eradicate polio worldwide continues while cases are still being detected in four countries – Afghanistan, Pakistan, Nigeria and India (no cases reported for over one year now).

Measles

Measles is a very common and contagious viral illness of childhood. In children, particularly those with malnutrition, it can be dangerous. Measles can cause deafness, blindness, encephalitis, and death.

Between 2000 and 2008, measles deaths dropped by 78 percent worldwide due to immunization. However, more than 20 million people continue to be infected by measles each year, resulting in 164,000 deaths in 2008, primarily among children.

German measles or rubella

This is a relatively mild viral illness of childhood. However, it can cause severe birth defects in children born to mothers who contracted the disease in the early stages of pregnancy. This is called congenital rubella syndrome.

The introduction of a rubella vaccine in 1969 has greatly reduced the incidence of congenital rubella syndrome in the developed world. Worldwide though the disease still causes approximately 110,000 cases each year, and causes blindness, deafness, and mental retardation in thousands more.

Diptheria

Diphtheria was once a dreaded bacterial illness. In the 1920s, diphtheria infected an estimated 100,000 to 200,000 people per year in the United States and killed 13,000 to 15,000. It is now rare in the United States but is responsible for about 5,000 deaths each year in developing countries, primarily among children.

Pertussis

Pertussis, or whooping cough causes spasmodic, uncontrollable coughing that persists for weeks. Before the arrival of the vaccine, pertussis infected an average of 200,000 people a year in the United States alone. Rates have declined with the rise of vaccination against the infection but pertussis still kills almost 195,000 people every year.

History of vaccines

The first vaccine developed was against smallpox by Edward Jenner, English "country" physician, in Berkeley. He found that dairy maids with cow pox were relatively immune to small pox. He took the exudates and secretions from a cowpox pustule on the hand of dairymaid Sarah Nelmes and inserted it into the arms of an 8 year old boy James Phipps on May 14, 1796.

The vaccination was effective since the boy did not catch small pox even when he was infected with small pox virus six weeks after the vaccination. Jenner published his findings in 1798. Despite opposition, vaccination soon became accepted practice.

Louis Pasteur

Louis Pasteur generalized Jenner's idea by developing what he called a rabies vaccine (now termed an antitoxin), and in the 19th century compulsory vaccination laws were passed. The golden age of vaccine development did not come until after World War II, when several new vaccines were developed in a relatively short period. Their success in preventing diseases such as polio and measles changed the history of medicine altogether.

Immunization campaigns

In 1967, the WHO spearheaded a massive immunization campaign against smallpox. Within ten years, this disease had been vaccinated out of existence.

Wild-virus polio, which once circulated widely in nearly every region of the world, is now present in only a handful of countries, without a case diagnosed in the United States since 1979.

Measles, mumps, rubella, diphtheria, and pertussis were reduced from frightening epidemics to rare outbreaks within a few decades.

Types of vaccines

Killed vaccines - Vaccines containing killed microorganisms. This includes vaccines against flu, cholera, plague, polio and hepatitis A
Attenuated – the vaccine contains live organisms that have been weakened to disable their virulent properties. Examples include: Yellow fever vaccine, rubella, measles, mumps, typhoid, tuberculosis (Bacillus Calmette Guerin or BCG) etc.
Toxoids – These are inactivated toxic compounds secreted by the organism. Examples include Diphtheria, tetanus etc.
Subunit vaccines – These contain part of the vaccine. Examples include: vaccine against Hepatitis B with protein subunits; the virus-like particle (VLP) vaccine against human papillomavirus (HPV) and the hemagglutinin and neuraminidase subunits of the influenza virus.
Conjugate vaccines – These contain the polysaccharide outer coats with proteins or toxins. Examples include ''Haemophilus influenzae'' type B vaccine.