Diseases That Vaccines Made You Forget About

Regardless of the current controversy surrounding the COVID-19 vaccines, public health experts agree that, throughout recent history, vaccines have saved millions of lives. In fact, a report published in The Lancet in January 2021 concluded that between 2000 and 2019, vaccinations for just 10 diseases saved the lives of roughly 37 million people in low- and middle-income countries. In the United States, vaccination efforts in just a 20-year span (1994-2013) are estimated to have saved the lives of some 732,000 children (via the Centers for Disease Control and Prevention).

In addition to COVID-19, there are 26 diseases for which a vaccine has been approved for use in the United States. Many of these, such as immunizations against polio, measles, and chickenpox, are given as part of a recommended vaccination schedule for infants and children. Others, such as the seasonal flu shot or the vaccine for pneumococcal disease, are also critical for keeping adults — particularly the elderly — healthy. Several, including typhoid fever and tuberculosis, are only recommended for Americans traveling to certain parts of the world or working in particular professions (via the CDC).

Thanks to widespread vaccination efforts, many diseases that were once common, particularly during childhood, have faded from our memory. However, it's important to acknowledge the toll such diseases took (and, in some cases, still take) and follow the recommended immunization schedule. Even if we've forgotten about them, most of these diseases still have the potential to become widespread again.

A brief overview of smallpox

Over the centuries, smallpox (caused by the variola virus) has killed millions of people. In just the 20th century, it claimed the lives of 300–500 million people worldwide; a staggering 10% of all deaths during that time period. However, smallpox is also the ultimate vaccination success story. To date, it remains the only human disease that has been completely eradicated from the planet (via the American Society for Microbiology).

Smallpox plagued humanity for at least 3,000 years. Approximately 30% of people who contracted this dreaded disease died, and survivors were often left horribly scarred. Initial efforts to curb the spread of smallpox focused on a process known as variolation, in which infectious material from a smallpox pustule was either scratched into a person's arm or inhaled. The individual would get smallpox, but usually a less severe case. Even so, variolation was a gamble, as some still died from exposure to the virus. In 1796, English doctor Edward Jenner began developing what would become the world's first vaccine.

Over the years, advancements in vaccine creation and delivery led to the disappearance of smallpox from North America in 1952 and from Europe in 1953. In 1959, the World Health Organization (WHO) began a campaign to eradicate smallpox from the rest of the world. The program was ultimately successful, and smallpox was officially declared "extinct" on May 8, 1980. There are, however, two laboratories that store samples of the variola virus for research purposes (via the CDC).

The eradication of polio

Polio (poliomyelitis) is a highly contagious viral infection that mostly affects children under age 5. It can cause fever, fatigue, headache, vomiting, stiffness of the neck, pain in the limbs, and paralysis. Approximately 1 in 200 cases result in irreversible paralysis, and 5–10% of those paralyzed die (via the WHO).

Jonas Salk developed the first polio vaccine, which was approved in 1955. This vaccine contained an inactivated (killed) virus. An oral polio vaccine developed by Albert Sabin containing a live attenuated (weakened) virus became available in 1961. Although vaccination efforts had widespread and enthusiastic public support, there was controversy over which vaccine was best. Research showed that in very rare cases, Sabin's live attenuated vaccine could cause polio with paralysis, so in 1999, Salk's inactivated vaccine became the preferred option in the United States (via the Science History Institute).

In the early 1950s, before the development of the polio vaccines, more than 15,000 children were paralyzed each year by polio. Cases dropped drastically after the release of the vaccines. No cases of polio have originated in the United States since 1979 (via the CDC). Even so, the polio vaccine is part of the standard childhood immunization schedule recommended by the CDC. This is because polio can still be brought into the United States by a traveler. It's usually given as a four-dose series at 2 months, 4 months, 6–18 months, and 4–6 years (via the CDC).

What is Haemophilus influenzae type b?

Haemophilus influenzae type b (Hib) is a bacteria that can infect the membrane that lines the brain, causing meningitis. Hib commonly lives in the nose and throat, and most adults are immune, but infants are not. Symptoms of Hib infection include fever, stiff neck, and drowsiness. Severe cases can lead to permanent paralysis, deafness, blindness, cognitive impairment, coma, and death. 

Before the development of an effective vaccine, Hib was the most common cause of meningitis (via Children's Hospital of Philadelphia). Pre-vaccine, Hib infected more than 20,000 children annually. As many as 1 in 5 suffered brain damage or deafness, and 5% died (via the CDC).

The first Hib vaccine became available in the United States in 1985, but wasn't very effective in children under 18 months of age. A more effective vaccine was approved in 1987. This immunization is a conjugate vaccine, which means it's made by chemically binding the polysaccharide (complex sugar) capsule that surrounds the bacteria to a protein. The vaccine doesn't contain any actual Hib bacteria (via the Immunization Action Coalition). Hib vaccines are part of the standard immunization schedule for children. Depending on the exact type of vaccine used, it's given either as a 4-shot series (at 2, 4, 6, and 12–15 months) or as a 3-shot series at 2, 4, and 12–15 months (via the CDC).

The discovery of a chickenpox vaccine

Chickenpox is caused by the varicella-zoster virus and is highly contagious. Most common in school-age children, it causes fever and an itchy rash that can result in several blisters. The infection lasts 5–10 days and is usually mild, but complications such as bacterial skin infections, pneumonia, and meningitis sometimes occur. 

Before the development of a chickenpox vaccine, approximately 100 Americans died of chickenpox each year. The varicella virus remains in the body forever, and in about one-third of individuals who've had natural chickenpox, it "reactivates" later in life and re-emerges as shingles. 

The chickenpox vaccine was first introduced in 1995. It uses a live attenuated (weakened) version of the virus and is 99% effective. Because the vaccine contains a live virus, in very rare cases, it can cause a mild case of chickenpox. It's also possible for vaccine recipients to develop shingles, but this is less likely than with naturally acquired chickenpox.

Today, the chickenpox vaccine is given as a 2-dose series, with the first shot at 12–15 months and a second shot between ages 4-6. It's also recommended for anyone over age 13 who never had natural chickenpox, as adult chickenpox is riskier. In these cases, the 2 doses are given 4–6 weeks apart (via the Immunization Action Coalition).

The introduction of the measles vaccine

Measles is a highly contagious viral infection (via Michigan Medicine). Symptoms appear 10–12 days after exposure and begin with a fever. A few days later, a rash appears, beginning at the hairline and traveling down the body. The rash usually lasts 5–6 days. Other symptoms include a cough, loss of appetite, and conjunctivitis. Complications occur in about 30% of cases and include diarrhea, ear infections, pneumonia, and encephalitis. Before the development of a vaccine, there were 3–4 million measles cases in the United States each year, leading to 6,000–12,000 deaths annually.

Two measles vaccines — one that used inactivated virus and another that used live attenuated virus — were developed in 1963. A better version of the live attenuated vaccine came into use in 1968, and in 1971, this vaccine was combined with vaccines for mumps and rubella. The combined measles mumps rubella (MMR) vaccine is given as a 2-shot series, with the first dose given at 12–15 months and the second dose given between ages 4-6.

Measles cases dropped dramatically after the introduction of the vaccine. By 2004, only 37 cases were reported. However, vaccination rates are now falling and cases are on the rise because parents aren't following the recommended immunization schedule for their children. Many of these individuals fear the MMR vaccine causes autism or other negative health effects, despite the fact that there is no credible scientific evidence to support such claims (via the Immunization Action Coalition).

A short history of mumps

Mumps was once a common childhood illness. It's a viral infection that causes a headache, low-grade fever, loss of appetite, and, in about 31–65% of cases, swelling of the salivary glands (parotitis). For most children, mumps is a mild illness. In fact, 15–27% of infected people have no signs or symptoms. It's also less contagious than measles and chickenpox, but complications can occur, including viral meningitis and inflammation of the testicles, ovaries, or breasts. In the case of testicular inflammation, pain can last for weeks. It can also lead to testicular atrophy and, in rare cases, infertility. Approximately 1 in 20,000 people with mumps will become permanently deaf in one or both ears because of the infection.

Before the creation of a mumps vaccine, more than 200,000 people got mumps each year. A vaccine was released in 1967, and in 1971, the combined measles, mumps, and rubella (MMR) vaccine was created. In 2005, varicella (chickenpox) was added to create the MMRV vaccine. Today, you can only be vaccinated against mumps through 1 of these 2 combination vaccines — there's no mumps-only vaccine. The MMR and MMRV vaccines use live attenuated versions of the mumps virus. Even after both doses, protection against mumps is only about 88%. Outbreaks do occasionally still occur. During years with outbreaks, total cases can rise to as many as 6,500 (via the Immunization Action Coalition).

Understanding and preventing rubella

Like measles and mumps, rubella used to be a very common childhood illness. Rubella is usually a mild disease, and as many as half of all infected individuals have no signs or symptoms. Children who do show symptoms typically develop a measles-like rash that starts on the face and travels down the body. In addition to the rash, older children and adults may also have a low-grade fever, swelling in the lymph nodes of the neck, and upper respiratory symptoms. Adult women who get rubella often experience pain and stiffness in the joints of their fingers, wrists, and knees. 

Complications from rubella include encephalitis and temporary drops in platelet levels. The most serious threat posed by rubella, however, is when a pregnant woman contracts the disease in the first trimester of pregnancy and passes it on to the fetus. Approximately 85% of infected fetuses will be born with congenital rubella syndrome (CRS), which can include deafness, vision issues, heart defects, and intellectual disability.

Thanks to the rubella vaccine, which was first created in 1969 and then combined with the vaccines for measles and mumps in 1971, rubella infections are now very rare in the United States. There is an average of only about 11 cases per year. About 5% of children develop a rash after receiving the MMR vaccine, but the rash is mild and the child isn't contagious (via the Immunization Action Coalition).

Exploring the cause of diphtheria

Diphtheria is caused by a toxin released by the bacteria Corynebacterium diphtheriae. Initial symptoms include sore throat, fever, and chills. The defining symptom of diphtheria, however, is the formation of a thick membrane that coats the back of the throat, which can make breathing difficult. Approximately 5–10% of people who contract the disease will die, and for some age groups, the mortality rate can be as high as 20%. The toxin can also paralyze the muscles that control breathing, and abnormal heart rhythms and pneumonia are possible.

A diphtheria antitoxin has been available since 1891, and the bacteria can also be killed with antibiotics. However, these treatments aren't always effective, so vaccination is the best option. The diphtheria vaccine was first created in 1921, but wasn't in widespread use until the 1930s. It's made by chemically treating the bacterial toxin that causes diphtheria. In the mid-1940s, the diphtheria vaccine was combined with vaccines for the toxins that cause tetanus and whooping cough. This combined vaccine is now given as a 4-shot series to infants at 2, 4, 6, and 15–18 months of age. Children should receive a booster dose between ages 4-6, and everyone should get a booster every 10 years. Thanks to vaccination, cases of diphtheria in the United States have become rare, falling from 100,000–200,000 each year in the 1920s (via the Immunization Action Coalition).

Avoiding and preventing tetanus

Tetanus, also called lockjaw, is caused by a toxin produced by the bacteria Clostridium tetani. These bacteria are found in the soil and produce spores that are difficult to kill. If the spores enter the human body, they can start producing the toxin that causes tetanus. This toxin attacks the central nervous system, causing muscle stiffness and spasms (usually beginning in the jaw), and difficulty swallowing. Other symptoms include fever, rapid heart rate, elevated blood pressure, and sweating. The spasms tetanus causes can be so severe that individuals may break their spines or arm and leg bones. Tetanus is fatal in 10–20% of cases, and for those who do survive, recovery can take months.

The first tetanus vaccine was created by chemically altering the toxin so that the body could build immunity. It was developed in 1924, and in the 1940s, it was combined with the vaccines that protect against diphtheria and whooping cough. Today, in addition to the 4-dose vaccination given to children, adults should receive a booster every 10 years. When someone has a wound that might lead to tetanus and it's been more than 5 years since their last tetanus booster (or if their vaccination status is unknown), doctors will often administer a booster just to be safe. In the late 1940s, there were 500–600 cases of tetanus each year. Thanks to widespread vaccination, there were only about 30 cases reported annually between 2016-2018 (via the Immunization Action Coalition).

Controlling whooping cough

Whooping cough is caused by a toxin produced by the bacteria Bordetella pertussis. The disease is divided into 3 stages. In the first, which lasts 1-2 weeks, individuals have basic respiratory symptoms like a runny nose, mild cough, and sneezing. The second stage usually lasts 1-6 weeks and is marked by bursts of rapid coughing. It is followed by a long and difficult inhalation that often produces a "whoop" noise, giving the disease its name. The final stage can last from 2 weeks to several months and include occasional coughing fits. Pertussis can be very serious, especially for infants younger than 6 months. It can cause bacterial pneumonia, seizures, reduced oxygen supply to the brain, and death. 

Before a vaccine was developed, there were about 200,000 cases of whooping cough each year, and it was a significant cause of infant mortality. The first pertussis vaccine was developed in the 1930s, and a version that causes fewer adverse effects was created in 1991 — it is the version most commonly used today. Like the vaccines for diphtheria and tetanus, the whooping cough vaccine is made by chemically altering the toxin so that the body develops immunity. The vaccine is only 80–85% effective against pertussis, and immunity decreases over time, so regular boosters are recommended.

Unfortunately, rates of whooping cough have been on the rise since the 1980s. In 2019, for instance, there were 15,662 cases of whooping cough and 9 deaths (via the Immunization Action Coalition).

Understanding pneumococcal disease

Pneumococcal disease is a collection of 3 diseases: pneumonia, bacteremia, and meningitis. It is caused by strains of the bacteria Streptococcus pneumoniae. Pneumococcal pneumonia causes fever, chills, chest pain, cough, shortness of breath, rapid breathing and heart rate, and weakness. Pneumococcus accounts for about 30% of all cases. Pneumococcal bacteremia, which is a blood infection without pneumonia in the lungs, is the most common form of pneumococcal disease in young children. Pneumococcal meningitis, an infection of the membrane that covers the brain, accounts for 50% of all bacterial meningitis cases. All 3 of these diseases can be life-threatening. Pneumococcal pneumonia has a mortality rate of 5–7%, while bacteremia caused by pneumococcus has a mortality rate of up to 60% in vulnerable populations. Pneumococcal meningitis kills about 8% of infected young children and 22% of infected adults.

Before the development of a vaccine, pneumococcal disease killed about 200 children under age 5 annually. Today, pneumococcus kills more than 3,500 people annually. The very young and the elderly are the most at risk. The pneumococcal polysaccharide vaccine (PPSV23) was first developed in the 1970s and improved in the 1980s. Today, it's usually given to adults over age 65 and younger individuals with certain underlying medical conditions or risk factors. The pneumococcal conjugate vaccine (PCV13) was created in the 2000s. It's the preferred vaccine for infants and is given as a 4-dose regimen at 2, 4, 6, and 12–15 months of age (via the Immunization Action Coalition).

Identifying and preventing hepatitis B

Hepatitis B is a viral liver disease that can be contracted after coming into contact with infected blood or certain bodily fluids. Unprotected sex and sharing needles or personal care items, like razors and toothbrushes, can result in transmission. Symptoms of hepatitis B include fever, joint pain, extreme fatigue, abdominal bloating and tenderness, loss of appetite, and jaundice (yellowing of the skin and eyes). While most people fully recover, the virus permanently remains in about 2% of adults, 30% of children ages 1-5, and 90% of infants under age 1 following initial infection. While the majority of people with chronic hepatitis B feel healthy, about 25% will eventually develop liver scarring, liver failure, or liver cancer.

The first hepatitis B vaccine became commercially available in 1982 and is considered highly effective. Proof of hepatitis B vaccination is often necessary to begin school. Thanks to immunization efforts, new cases of hepatitis B have fallen dramatically among children and teens. Even so, there are as many as 1.4 million Americans living with chronic hepatitis, and many die each year as a result of hepatitis B–related liver disease (via the Immunization Action Coalition).

Because of the high risk of lifelong infection if exposed to hepatitis B as a newborn, the recommended vaccination schedule for children begins at birth, with the first dose usually given in the first 24 hours after delivery. Revaccination usually isn't necessary later in life (via the CDC).

The development of the rotavirus vaccine

If you're old enough to be reading this, chances are you had rotavirus as an infant or young child. In fact, according to the Immunization Action Coalition, "virtually everyone in the world is infected by rotavirus disease by age five years." This is changing, however, because of 2 rotavirus vaccines developed in 2006 and 2008 that are now part of the standard schedule of childhood immunizations.

Rotavirus infection causes fever, vomiting, and diarrhea, and usually lasts 3-7 days. For infants (the age group most affected), this triple threat of symptoms can quickly lead to dehydration, which can become life-threatening. Prior to the development of a vaccine, rotavirus caused 200,000 emergency room visits, 55,000–70,000 hospitalizations, and 20–60 deaths annually in the United States. The vaccines, which are given orally in either a 2-dose regimen at 2 and 4 months or a 3-dose regimen at 2, 4, and 6 months depending on the vaccine, are very effective. They prevent 74–87% of all rotavirus infections, and 85–98% of serious cases. Both vaccines currently in use are considered very safe. However, a previous rotavirus vaccine, released in 1998 and quickly withdrawn in 1999, was found to cause intussusception (a type of intestinal obstruction) in rare cases.

Examining the rabies vaccine

If you saw the movie "Cujo," you know how scary rabies is. This viral infection is so deadly that once you start showing symptoms, it's almost always fatal. Humans get rabies from the saliva of an infected animal. Domestic animals that can carry rabies include dogs, cats, ferrets, cows, horses, and goats. Wild animals, such as bats, raccoons, foxes, coyotes, and skunks, can also carry rabies. Symptoms in humans include fever, headache, vomiting, difficulty swallowing, agitation and hyperactivity, excessive salivation, fear of water, hallucinations, paralysis, and, ultimately, death in 1-2 weeks. If treatment in the form of rabies immune globulin and a series of 4 rabies vaccines is begun immediately after exposure, the disease can be controlled (via the Mayo Clinic).

Although rabies vaccines are typically only given to humans in the United States if they've had known or suspected exposure to rabies, pet vaccination has played a huge role in virtually eliminating rabies across the country. Globally, 98% of human rabies cases result from dog bites, and at the turn of the 20th century, canine rabies virus variant (CRVV) was common in the United States. Widespread vaccination of pets began in 1947, and by the late 1960s, fewer than 500 rabid dogs and 3 human cases were reported each year. Today, there is an average of only 2 deaths per year in the United States from rabies. Bats are now the leading cause of rabies deaths in humans in the United States (via the CDC).