Before the late 18th century, Americans had minimal defense against devastating infectious diseases such as smallpox, measles, and diphtheria. However, over the subsequent 250 years, vaccines played a pivotal role in either eradicating or significantly reducing many preventable infectious diseases, thereby averting millions of cases, infections, and fatalities.
According to health experts, vaccines are engineered to trick the immune system into believing it has encountered a specific disease. This process generates an 'immune memory,' enabling the body to mount a robust immune response should the actual pathogen appear. While true vaccines can have side effects and a risk of injury, the collective benefit to individuals and society far outweighs any potential harm, as noted by medical commentator, Dr. Marc Siegel.
As the United States approaches its 250th anniversary, certain vaccines stand out as some of the most profound medical achievements in the nation's history.
Early Triumphs: Eradicating and Controlling Deadly Diseases
Smallpox: A Global Eradication Story
Smallpox, a highly contagious viral disease caused by the variola virus, was once among the deadliest diseases globally. Before vaccination, it claimed the lives of approximately 30% of those infected, according to data from the Centers for Disease Control and Prevention (CDC). This infectious illness had no cure and spread through close person-to-person contact, leading to fever, fatigue, and a distinctive rash that developed into pus-filled blisters. Survivors frequently endured permanent scarring or blindness.
The first successful vaccine, developed by English physician Edward Jenner in 1796, ultimately revolutionized public health in the United States. Jenner's smallpox vaccine eventually led to the global eradication of smallpox, a monumental achievement recognized by the World Health Organization. Today, the vaccine is no longer routinely administered to the general public and is primarily reserved for specific military, laboratory, and emergency response applications.
Rabies: Post-Exposure Prevention
Rabies, a viral disease that attacks the brain and nervous system, is transmitted through the saliva of infected mammals, most commonly via bites from dogs, bats, raccoons, skunks, and foxes. Once symptoms manifest, rabies is almost invariably fatal, according to the National Institutes of Health (NIH). Although there is no cure for the disease once symptoms appear, prompt vaccination immediately following exposure can prevent its development. It can also be administered before exposure to individuals at high risk.
Researcher Louis Pasteur developed the first rabies vaccine in 1885, as documented by The Children's Hospital of Philadelphia (CHOP). Today, immediate vaccination after exposure remains the standard protocol to prevent this otherwise nearly universally fatal disease.
Diphtheria: A Childhood Scourge Contained
Diphtheria is a bacterial infection capable of causing a thick coating in the throat. It proved fatal for some, and survivors could face severe complications, including heart damage, paralysis, and breathing difficulties, according to the CDC. Before the vaccine's introduction in the 1920s, diphtheria was a leading cause of illness and death among young people in the U.S. During that decade, between 100,000 and 200,000 cases and 13,000 to 15,000 deaths were recorded each year, predominantly affecting children.
The diphtheria toxoid vaccine was introduced in the 1920s. Thanks to widespread vaccination, diphtheria is now exceedingly rare in the U.S., as confirmed by the CDC. The vaccine remains a component of the routine childhood immunization schedule as part of the DTaP series, with booster doses recommended for teenagers, adults, and pregnant women.
Tetanus: Preventing "Lockjaw" and Fatal Spasms
Tetanus is a bacterial disease caused by Clostridium tetani, which enters the body through cuts or wounds, according to the CDC. The infection can result in severe muscle spasms, a condition known as "lockjaw," and can be fatal. Prior to vaccination, tetanus was often deadly because severe muscle spasms could render swallowing or breathing impossible. Although the disease does not spread from person to person, hundreds of Americans succumbed to tetanus annually, historical records indicate.
The tetanus toxoid vaccine was developed in the 1920s, according to CHOP. Tetanus vaccination continues to be a part of the routine childhood immunization schedule, with booster shots advised every 10 years and as needed following certain types of wounds.
Whooping Cough (Pertussis): Protecting Infants and Communities
Whooping cough, or pertussis, is a highly contagious bacterial infection that triggers severe coughing fits, often making it difficult to breathe, eat, or sleep. Infants face the highest risk, as they can develop complications such as pneumonia, seizures, brain damage, or even death. Before widespread vaccination, the U.S. reported over 200,000 pertussis cases and thousands of pediatric hospitalizations each year, the CDC states.
The initial pertussis vaccine was introduced in the 1910s, followed by the combination DTP (diphtheria, tetanus, and pertussis) vaccine in the 1940s. Following widespread vaccination efforts, cases plummeted by more than 90%, and deaths from the disease became uncommon. The pertussis vaccine remains a part of the routine U.S. immunization schedule for children, adolescents, and adults, and medical professionals recommend vaccination during pregnancy to transfer protective antibodies to newborns.
Broader Protection: From Seasonal Illnesses to Childhood Diseases
Influenza: Battling Seasonal Epidemics
This contagious viral respiratory illness can lead to serious complications, hospitalization, and death, as CDC data demonstrates. Before the vaccine became available, seasonal flu epidemics caused widespread illness and mortality every year. During the 1918 influenza pandemic, often referred to as the "Spanish flu," an estimated one-third of the global population was infected, and at least 50 million people died worldwide, including approximately 675,000 Americans.
The first U.S. flu vaccine was licensed in 1945, initiating routine seasonal influenza vaccination programs. Widespread vaccination has significantly diminished the risk of flu illness, hospitalization, and death. The CDC advises that everyone aged 6 months and older receive a seasonal flu vaccine annually, with only rare exceptions. The vaccine is updated each year to target evolving strains.
Polio: Eliminating a Paralytic Threat
Polio, or poliomyelitis, is a highly contagious viral disease caused by the poliovirus, primarily spreading through contact with contaminated food, water, or stool, according to the CDC. For some individuals, the virus can attack the nervous system, resulting in permanent paralysis, breathing difficulties, and death. In the early 1950s, more than 15,000 cases of paralytic polio were reported annually in the U.S.
In 1955, Jonas Salk’s polio vaccine was introduced in the country, leading to a dramatic reduction in case counts. By 1979, the U.S. was declared free of wild poliovirus, according to the World Health Organization. Injected polio vaccination continues to be a part of the routine childhood U.S. immunization schedule.
Measles, Mumps, and Rubella (MMR): A Combined Defense
Before the advent of vaccines, measles, mumps, and rubella were prevalent childhood diseases that infected millions of Americans and could trigger severe complications. Prior to the measles vaccine, almost all American children contracted this highly contagious viral disease by age 15, according to the NIH. Annually, approximately 400 to 500 Americans died from measles, while about 1,000 experienced brain swelling, and 48,000 were hospitalized, records show.
Before the first mumps vaccine, about 186,000 cases were reported in the U.S. each year, and the disease was a common cause of meningitis in children, as per the NIH. Rubella epidemics also regularly occurred in the U.S. before vaccination. Between 1964 and 1965, approximately 12.5 million Americans were infected, leading to around 2,100 newborn deaths and 20,000 babies born with congenital rubella syndrome, which caused blindness, deafness, heart defects, and developmental disabilities.
The measles vaccine was introduced in 1963, followed by mumps in 1967 and rubella in 1969. In 1971, the MMR (measles, mumps, and rubella) vaccine became available, offering protection against all three contagious viral diseases in a single injection. Before the combined vaccine, children typically required three separate shots, the CDC noted. Widespread vaccination has reduced cases of all three diseases by more than 99% in the United States, according to NIH data.
Measles was declared eliminated in the U.S. in 2000, signifying that it was no longer continuously spreading within the country. Routine vaccination also led to the declaration of endemic rubella's elimination in the U.S. in 2004.
Hepatitis B: Protecting Against Liver Disease
Hepatitis B, a viral infection that targets the liver, spreads through contact with infected blood and other bodily fluids, according to the CDC. Some individuals develop chronic hepatitis B, which can progress to cirrhosis, liver failure, and liver cancer. Before vaccination, hepatitis B posed a significant public health threat in the U.S. In the early 1980s, an estimated 200,000 to 300,000 Americans contracted the infection annually, the NIH states. Infants infected at birth were at a particularly high risk, with about 90% developing chronic infection.
The hepatitis B vaccine was licensed in 1981, and the CDC began recommending universal infant vaccination in 1991. Since then, acute hepatitis B cases have decreased by more than 80% in the U.S., and infections among children and adolescents have fallen by over 95%, as per the NIH.
Haemophilus influenzae type b (Hib): Reducing Childhood Infections
Haemophilus influenzae type b (Hib) is a bacterial infection that can cause pneumonia, meningitis, bloodstream infections, and severe throat swelling, according to the CDC. Severe cases can result in hearing loss or brain damage. Hib was once the primary cause of bacterial meningitis in young children in the U.S., with approximately 20,000 serious infections and 1,000 deaths reported each year in children aged 5 and younger.
The first Hib vaccine was licensed in 1985, and routine immunizations have since reduced invasive disease by more than 99%, according to CDC data. The infection is now rare in the U.S.
Advanced Immunizations: Modern Defenses and Cancer Prevention
Chickenpox (Varicella): Taming a Common Childhood Illness
Chickenpox (varicella) is a highly contagious viral disease caused by the varicella-zoster virus, which produces an itchy, blister-like rash, fever, and fatigue, according to the CDC. In some individuals, it can lead to serious complications, including pneumonia, brain inflammation, and bacterial skin infections. Before the first chickenpox vaccine became available in the U.S. in 1995, about four million Americans were infected each year, resulting in approximately 100 to 150 deaths and up to 13,000 hospitalizations, as reported by the CDC and NIH.
Since routine two-dose childhood vaccination commenced, hospitalizations and deaths have declined by more than 90%, and severe complications have become rare, CDC data indicates.
Hepatitis A: Preventing Liver Infection Outbreaks
Hepatitis A, a highly contagious viral liver infection, spreads primarily through contaminated food or water or close contact with an infected person, as per the CDC. While it does not cause chronic liver disease like hepatitis B, it can lead to weeks or months of illness and, in rare instances, liver failure. Before vaccination, outbreaks caused as many as 30,000 infections annually.
The first hepatitis A vaccine was licensed in the U.S. in 1995. Since routine childhood vaccination began, infection rates have dropped by more than 95%, according to the NIH.
Pneumococcal Disease: Protecting Against Bacterial Complications
Pneumococcal disease, caused by the bacterium Streptococcus pneumoniae, can lead to pneumonia, meningitis, bloodstream infections, ear infections, and sinus infections, the CDC states. Before vaccination, pneumococcal disease caused thousands of cases of meningitis and bloodstream infections and hundreds of deaths among young children, as per the NIH. Older adults also faced a high risk of hospitalization from bacterial pneumonia.
The first pneumococcal conjugate vaccine was licensed in 2000. Routine childhood vaccination has dramatically reduced disease rates, and newer vaccines have been developed to protect against emerging bacterial strains.
Human Papillomavirus (HPV): The First Cancer-Preventing Vaccine
The human papillomavirus (HPV), the most common sexually transmitted infection in the U.S., can cause cervical, anal, penile, vaginal, vulvar, and oropharyngeal cancers, according to the CDC. The HPV vaccine was licensed in 2006, marking it as the first immunization specifically designed to prevent multiple types of cancer. Since the vaccine's introduction, HPV infections, precancers, and genital warts have significantly declined, CDC data shows.
HPV vaccination is now part of the routine U.S. immunization schedule, with two doses recommended for those younger than 15 and three doses for individuals aged 15 and older.
Rotavirus: Combating Severe Diarrhea in Infants
Rotavirus is a highly contagious virus that primarily affects infants and young children, causing severe diarrhea, vomiting, and fever. Before the vaccine became available in 2006, nearly every child contracted the virus by age 5, often leading to severe dehydrating diarrhea, the CDC states. Up to 70,000 children were hospitalized and 20 to 60 died each year in the U.S.
Since routine rotavirus vaccination began, hospitalizations, emergency room visits, and severe illness have significantly declined. Infants receive two or three oral doses as part of the routine immunization schedule.
Shingles: Alleviating Painful Reactivations
Shingles is a painful rash caused by the reactivation of the varicella-zoster virus, the same virus responsible for chickenpox, as per the CDC. It can cause severe nerve pain that may persist for months or even years. Before the vaccine was available, about one million Americans developed shingles each year, with adults over age 50 facing the highest risk.
The first shingles vaccine was licensed in 2006, and the more effective Shingrix vaccine was introduced in 2017, substantially reducing the risk of shingles and long-term nerve pain, according to the CDC and FDA. Experts recommend two doses for adults aged 50 and older and for certain immunocompromised adults aged 19 and older.
COVID-19: A Rapid Response to a Global Pandemic
When the COVID-19 pandemic spread worldwide in 2020, there was no vaccine to prevent severe illness from the infection, which is caused by the SARS-CoV-2 virus. In the U.S., the contagious virus led to millions of hospitalizations and over 1.2 million deaths, according to data from the CDC and NIH. The first COVID-19 vaccines received emergency authorization in December 2020. Multiple studies have demonstrated that the vaccines significantly reduce the risk of severe illness, hospitalization, and death, particularly among high-risk groups.
COVID vaccines saved millions of lives around the world during the COVID pandemic.
Although the CDC continues to recommend COVID-19 vaccination, specific guidance varies by age, risk level, and previous vaccination history.
A medical expert, whose company is actively involved in developing a universal flu vaccine among other immunizations, summarized the profound impact of these and other vaccines in America. He advised,