In light of President Obama’s declaration of “national emergency” imposed by the outbreak of the H1N1 virus, Surprising Science is setting this week aside to discuss the history and science of vaccines and their importance in battling viruses and diseases, including swine flu. See yesterday’s post for part 1, A Brief History and How Vaccines Work.
Smallpox: Once one of the world’s most dreaded diseases, smallpox killed as many as 30 percent of people who became infected with it and left survivors deeply scarred; no effective treatment was ever found. English physician Edward Jenner in 1796 discovered how to use cowpox virus to vaccinate individuals against smallpox. Vaccination efforts grew over the next century. The last reported case in the United States occurred in 1949, and vaccination ended here in 1971. The last case of smallpox in the world occurred in Somalia in 1977, and the disease was declared to be eradicated in 1980.
Polio: The virus mainly attacks children under the age of three, and infection can result in severe paralysis and death. Vaccines developed in the 1950s and 1960s have eliminated the disease from much of the world. However, cases are still found in several countries, and immunization efforts continue in Africa and Asia.
Measles: Measles is a respiratory disease that is accompanied by a rash. In the United States and other countries where measles vaccination is common, incidence of the disease has become rare, which is good because it can lead to pneumonia, encephalitis or death. Worldwide, there are about 10 million cases of measles each year and 197,000 deaths. But if there were no vaccinations, the World Health Organization has estimated that 2.7 million people would die of the disease each year.
Hib meningitis: The bacterium Haemophilus influenzae type b causes meningitis and pneumonia. It used to be the leading cause of bacterial meningitis in children. However, since the development of vaccines for the disease in the 1990s, it has been nearly eliminated in industrialized nations. The story isn’t so positive in the developing world, though. There, Hib infects about three million individuals and kills about 386,000 each year, mostly children under the age of five.
Tetanus: “He stepped on a rusty nail and died” was once a common epitaph. Tetanus, also called lockjaw, isn’t actually caused by the rust; it’s caused by the spores of the bacterium Clostridium tetani. A person becomes infected when dirt enters a wound. Babies can also become infected at birth following a delivery under non-sterile conditions. Infection results in stiffness, muscle spasms and, about a fifth of the time, coma and death. With increased rates of vaccination, though, incidence of the disease is declining worldwide.
Diphtheria: This upper respiratory tract infection is caused by the Corynebacterium diphtheriae bacterium. It has a fatality rate of about 5 to 10 percent, though that rate climbs to 20 percent among the very young and the elderly. Vaccination has driven the incidence of the disease in the United States from hundreds of thousands of cases per year in the 1920s to just a handful of cases today.
Tomorrow—Vaccine Week, Day 3: A History of Vaccine Backlash