Vaccines: From the 15th Century to Present Day

With a history dating back to at least the 15th century, vaccines are used to protect against upwards of 20 diseases today.

A study led by the World Health Organization (WHO) found that global immunization efforts have saved an estimated 154 million lives over the past five decades — 101 million of those lives were infants. The study found that vaccination against 14 diseases, including diphtheria, measles, meningitis A, pertussis, polio, and rubella, has “directly contributed to reducing infant deaths by 40% globally.”

People in different parts of the world have tried to prevent illness by intentionally exposing people to smallpox from at least the 15th century, according to WHO, in a practice called variolation. English physician Edward Jenner created the first successful vaccine in 1796, WHO reported, when he discovered that people infected with cowpox were immune to smallpox. The term vaccine was coined later, taken from vacca — the Latin word for cow.

The first influenza vaccine was approved for military use by 1945, followed by civilian use approval in 1946, according to information from WHO. This effort was led by doctors Thomas Francis Jr and Jonas Salk, who were closely associated with the polio vaccine, with the first effective polio vaccine developed by Salk from 1952 to 1955.

Today, vaccines help protect against more than 20 diseases, including pneumonia, cervical cancer, and Ebola.

Herd Immunity occurs in a population when enough people in a group or area have immunity to a germ, including a virus, so that it no longer can spread easily, a report by Cleveland Clinic explained. This often results from a combination of people getting vaccinated and people who get infected with the germ.

Herd Immunity has been achieved in the past for diphtheria, measles, polio, rubella, and smallpox, the Cleveland Clinic report continued. Most have been eliminated in “many countries worldwide” due to vaccination and other public health efforts, but until a disease has been determined eradicated, it can begin spreading to people who have not been vaccinated or infected previously.

A 2019 Gallup poll conducted in the United States found that 84% of respondents believe it is “very” or “extremely” important that parents vaccinate their children. This matches a previous Gallup poll from 2015, but was down from 94% in 2001. 

Since vaccines were first introduced, questions regarding their benefit and safety have persisted, according to the book “Vaccines: What Everyone Needs to Know.” As widespread vaccination has caused a decrease in vaccine-preventable diseases, public concern over the threat of the diseases has also decreased, the author wrote. 

Additionally, WHO reported that one in five children still go unvaccinated in “many parts of the world.” In 2024, 14.3 million infants did not receive an initial dose of diphtheria, tetanus, and pertussis (whooping cough) vaccine, which, according to WHO, points to a lack of access to immunization and other health services. An additional 5.6 million are partially vaccinated. Of the total, 55% of the children live in 10 countries, including Ethiopia, Indonesia, and Sudan, according to WHO.

The United States Food and Drug Administration (FDA) approved the measles-mumps-rubella (MMR) vaccine in 1971, combining three vaccines that had been previously approved, according to Johns Hopkins Bloomberg School of Public Health.

British gastroenterologist Andrew Wakefield and colleagues published an article in The Lancet medical journal in 1998, presenting a series of 12 children who they reported developed gastrointestinal symptoms and autistic behaviors, with 8 patient’s parents reporting that symptoms developed after they received the MMR vaccine, according to “Vaccines: What Everyone Needs to Know.” At the time, the vaccine contained thimerosal, which has been used as a preservative in vaccines, as reported by the FDA. The use of thimerosal has “markedly declined” due to reformulation and development of vaccines in “single-use presentations.”

It was hypothesized in the article that the MMR vaccine may have prompted the production of antibodies that led to the behavioral changes after they attacked the nervous system, the book continued. Following the study, others hypothesized autism could be caused by thimerosal.

The study’s authors acknowledged that it did not prove an association between the vaccine and autism, but the lead author “went far beyond the paper’s conclusions in a press release and ongoing interactions with the media,” read a report by Johns Hopkins Bloomberg School of Public Health - Institute for Vaccine Safety. Wakefield’s license to practice medicine in the UK was revoked in 2010 and his study was retracted by The Lancet, the report continued.

The National Academy of Medicine (previously the Institute of Medicine) concluded “the body of evidence favors rejection of a causal relationship between autism and MMR vaccine and thimerosal-containing vaccines,” according to Johns Hopkins.

The Centers for Disease Control and Prevention (CDC) reported that “any vaccine can cause side effects,” but they are mostly minor, including a sore arm or low-grade fever, and go away within a few days. The CDC maintains a list of licensed vaccines in the United States, as well as side effects associated with each. The information is compiled from the CDC’s Vaccine Information Statements, which are derived from the Advisory Committee on Immunization Practices’ recommendations. CDC reported that “vaccines are continually monitored for safety.”