> Estimated deaths before widespread immunity: 300 million in the 20th century
> Vaccine introduced: 1796
> Vaccine impact: 5 million lives a year saved
There are theories that smallpox originated in the third century B.C. in Egypt, but the disease’s exact origin is unknown. Smallpox, which caused a high fever and a rash over the skin, killed nearly one in every three people who contracted it. Death toll estimates vary, but the most cited figure is 300 million in the 20th century alone. Transmission was through close contact or touching contaminated fabric.
While there have been earlier reports of relatively successful inoculation methods in Asia and Africa, it wasn’t until the late 18th century that Edward Jenner, an English doctor, was able to derive a smallpox vaccine. There were vaccination efforts in different parts of the world throughout the next century and a half, but still some 50 million were infected each year. The vaccine has also improved over time, and by the 1960s the World Health organization embarked on a global eradication campaign that lasted until the late 1970s. The WHO declared smallpox eradicated in 1980. Today, the deadly virus is known to exist only in secured laboratories in the United States and Russia.
Pertussis (Whooping cough)
> Estimated deaths before widespread immunity: 160,000 a year worldwide
> Vaccine introduced: 1914
> Vaccine impact: 160,700 lives a year saved
Pertussis is also known as the “100-day cough” because the infection can last for 10 weeks or longer. The disease, whose symptoms include coughing fits, is most dangerous for babies. It can cause serious complications particularly in children and babies, including pneumonia, apnea, and death. Whooping cough epidemics have been recorded since the Middle Ages. A vaccine was developed in 1914 and was later combined with tetanus and diphtheria shots to become widely available.
The Cleveland Clinic estimates that more than 160,000 lives a year have been saved since the vaccine was introduced more than a century ago. Before the vaccine, there were about 200,000 pertussis cases a year in the United States alone compared with just over 13,500 a year nowadays. Two pertussis vaccines are administered over the course of a child’s first 12 years of life to help protect against whooping cough, though they don’t offer lifetime protection. A booster dose is recommended for preteens at 11 or 12 years of age.
> Estimated deaths before widespread immunity: 787,000 a year worldwide
> Vaccine introduced: 1924
> Vaccine impact: 96% reduction in mortality since 1988
Tetanus is a bacterial infection that has no cure. It affects the nervous system, leading to painful muscle spasms, jaw cramping, fever, and seizures, among other symptoms. Complications can include broken bones, pulmonary embolism, and difficulty breathing that can be fatal in 10% to 20% of cases.
The disease-causing bacteria can be found in soil and can enter the body through a cut or a burn. About 34,000 newborns died from neonatal tetanus worldwide in 2015, a 96% reduction since 1988, when an estimated 787,000 babies died from the infectious disease. The reduction was largely due to scaled-up immunization, according to the WHO.
A tetanus vaccine was developed in the mid-1920s and became widely available in 1938. A few years later, it was combined with other vaccines. Today, tetanus toxoid-containing vaccines, such as variations of the combined diphtheria, tetanus, and pertussis vaccines, are included in routine immunization programs. Boosters vaccines are recommended every 10 years in order to maintain protection against the infection, though some research suggests a booster shot is needed every 30 years.
> Estimated deaths before widespread immunity: 15,000 Americans in the 1920s
> Vaccine introduced: 1921
> Vaccine impact: Almost 100% decrease in cases
Diphtheria, which spreads by airborne droplets or saliva, is a bacterial infection of the nose and throat that can obstruct swallowing and breathing and cause severe complications including paralysis, nerve damage, pneumonia, and death. The disease was a major cause of death among children before a vaccine was developed in 1921. That year, more than 15,000 children died from diphtheria and about 206,000 were infected in the United States alone. Between 2004 and 2017, there were only two cases of diphtheria nationwide, according to the CDC.
Though the total number of cases has significantly dropped since the 1920s, the death rate has not changed much and remains at about 5% to 10%. It may reach higher than 20% in children younger than 5 years and adults older than 40 years. People who contract the infection are treated with antibiotics.
> Estimated deaths before widespread immunity: 2.6 million a year worldwide
> Vaccine introduced: 1963
> Vaccine impact: 23.2 million lives saved between 2000-2018
Measles, a severe infection that causes high fever and red, blotchy skin rash and attacks the respiratory tract, is one of the most contagious viral diseases in existence. About 4 million cases were reported every year until a vaccine was introduced in 1963. The mortality rate is 1 to 2 per 1,000 cases. Overall, the number of infected people has gone down as vaccination has become common or, in some countries, mandatory. Immunization has resulted in an 84% drop in deaths from the infection between 2000 and 2016 worldwide, preventing 20.4 million deaths worldwide. In the United States, the MMR vaccine against measles, mumps and rubella is required for children attending public schools.
While the benefits of immunizations are very well established, there is a growing movement in America and across the world against vaccinations. Numerous studies, including recent research published in the journal PLOS Medicine, have found a higher prevalence of infections in urban areas that allow for nonmedical exemptions — rules that permit parents not to vaccinate their kids based on their beliefs. A 2018 global measles outbreak killed more than 140,000 people, most of them children under 5, according to the WHO and the CDC.