Vaccination: Increasing Your Shot at a Long, Healthy Life

Vaccinations save lives. It doesn’t get much simpler than that. Today, vaccinations exist for a variety of diseases, including measles, tetanus, and everyone’s least favorite wintertime malady, influenza (i.e., the flu). But how are these vaccines developed? More important, are they safe?


A number of illnesses and diseases can be prevented through vaccination. (Photo credit: Richard Shock/Corbis)

Benefits of Vaccines

A number of diseases and illnesses can be prevented through vaccination. Vaccination stimulates the bodys immune system to recognize future encounters with disease organisms and protect the body from infection. Immunization programs have helped to make the occurrence of certain once-epidemic diseases, such as polio, now very rare. But even when disease rates are low, immunizations are still recommended to prevent a resurgence. All vaccines that are widely deployed are rigorously tested for safety and effectiveness and are continuously monitored to ensure their efficacy. Today, diseases which once affected hundreds of thousands of infants, children, and adults, leading to thousands of deaths, are under control with the help of immunization programs.

What is Herd Immunity?

Vaccines are particularly important due to their ability to confer herd immunity, also called community immunity. Basically, herd immunity means that, when a significant portion of a community is immunized against a contagious disease, the majority of community members are protected because there is little chance of an outbreak. Herd immunity is particularly important because it confers protection to those who are unable to be immunized, such as newborn babies, pregnant women, and immunocompromised individuals.

When the majority of a community is not immunized against a disease, the threat of infection is much greater. In recent years, some communities have experienced whooping cough epidemics, in part due to there being a larger percentage of unvaccinated individuals.

Vaccine History

While there is evidence that the Chinese practiced inoculation against smallpox as early as 1000 CE, Edward Jenner, a British doctor, is often credited with developing the first vaccine. In 1796 Jenner successfully inoculated an eight-year-old boy against smallpox disease using a cowpox pustule. Cowpox refers to a skin disease, as well as the virus that causes it, that occurs in humans and other animal species. Cowpox is similar to smallpox but is much milder. Jenner believed that, by exposing patients to the milder cowpox virus, they would also develop immunity to smallpox. (The term vaccine comes from the Latin word vacca, which means cow.) As use of the vaccine became more widespread, smallpox was declared eradicated by the World Health Organization in 1980.

In the late 1800s, vaccines were developed for rabies, typhoid, cholera, and plague, though none became common in use until after 1900. In the 1920s, vaccines were developed for diphtheria, pertussis (whooping cough), tetanus, and tuberculosis. The period between 1945 and 1985 saw the development of 12 vaccines, including vaccines for influenza, polio, measles, mumps, rubella, and meningitis. The table below shows the vaccines currently used in the United States and notes the year each was introduced.

Vaccines Used in the United States (year first available)
anthrax (1970) Japanese encephalitis (1992) rotavirus (1998)
chickenpox (1995) measles (1963) rubella (1969)
diphtheria(1923) meningococcal (1975) shingles (2008)
hepatitis A (1995) mumps (1967) tetanus (1927)
hepatitis B (1981) pertussis (1926) tuberculosis (1927)
HIB (1985) pneumococcal (1977) typhoid fever (1896)
HPV (2006) polio (1955) yellow fever (1953)
influenza (1945) rabies (1885)

There are 23 vaccines currently licensed for use in the United States. The CDC provides a schedule of vaccines for infants and children (newborn to age 6), preteens and teenagers (ages 7 to 18), and adults (19 and older). You can find the recommended vaccines or booster shots for your age group in the More to Explore section at the bottom of this article.

How Are Vaccines Developed?

Before being released to the public, vaccines must first go through rigorous and extensive testing to ensure their safety and efficacy. Aside from the Food and Drug Administration (FDA), the Centers for Disease Control (CDC) and National Institute of Health (NIH) are also involved in ensuring vaccine safety. Developing a new vaccine is typically a long process. Following the exploratory and pre-clinical phases, the vaccine enters the three-stage clinical process, which is dependent on volunteers. In the first stage, a trial vaccine is given to small groups of people. In the second stage, the vaccine is given to people with characteristics (age, health) similar to those expected to receive the vaccine. In the third stage, thousands of people are given the vaccine. Following these clinical trials, the vaccine goes through formal regulatory review and approval, after which it is manufactured and made available to the general public or the vaccines intended audience. Even after receiving approval from the FDA, vaccines continue to be monitored for their safety and effectiveness. Although complications from vaccines are not unknown, they are extremely rare in occurrence.

Different Types of Vaccines

There are four main types of vaccines: live, attenuated vaccines; inactivated vaccines; toxoid vaccines; and subunit and conjugate vaccines.

  • Live, attenuated vaccines contain a version of the living microbe that has been weakened in the laboratory so that it cannot cause disease. The vaccines provoke strong cellular and antibody responses in the body and typically provide life-long immunity following one or two doses. The measles, mumps, and rubella (MMR) vaccine is an example of a live, attenuated vaccine.
  • Inactivated vaccines are made by killing the disease-causing microbes with the help of chemicals, heat, or radiation. The flu vaccine in the shot form is an example of an inactivated vaccine. This technique destroys the microbes ability to replicate but leaves it intact so that it can still be recognized by the immune system.
  • Toxoid vaccines are similar to inactivated vaccines, except that, rather than deactivating a microbe, a toxin produced by the microbe is inactivated. The body establishes an immune response to the markers for that toxin without being exposed to it. The tetanus shot is an example of a toxoid vaccine.
  • Subunit and conjugate vaccines are similar in that both contain specific pieces of the pathogens they protect against. Subunit vaccines contain only the antigens that best incite an immune system response. Some subunit vaccines are made by genetic engineering techniques; these vaccines are called recombinant subunit vaccines. The HPV vaccine is an example of a recombinant subunit vaccine. Conjugate vaccines are constructed from the coats of bacteria. These bacterial coats are combined with carrier proteins to elicit a strong immune response. The pneumococcal vaccine is an example of a conjugate vaccine.

Vaccine Safety

Questions concerning the safety of the MMR vaccine were brought to the surface in 1998 by Andrew Wakefield, at the time a senior lecturer at London’s Royal Free Hospital School of Medicine. Wakefield, along with 12 co-authors, published a study in the medical journal The Lancet that studied 12 children with autism. In the article, the researchers concluded that there was a link between the MMR vaccine and the onset of autism and bowel disease. The articles conclusions were immediately controversial. Other scientists were unable to replicate Wakefield’s results in subsequent studies. Questions arose as to potential conflicts of interest, improper labeling of study samples, and ethics violations. In 2010, The Lancet retracted the study, citing ethical misconduct. Ten of the 13 authors of the article have also since retracted their findings. Wakefield, who currently resides in the United States, has been barred from practicing medicine in the United Kingdom, and is not licensed to practice medicine in the U.S.

Unfortunately, the Wakefield study continues to impact vaccination rates. With the help of celebrity endorsement of the erroneous idea that vaccines are linked to autism, vaccination rates plummeted in the decade following the Wakefield study. A recent study indicates that in certain wealthy Los Angeles neighborhoods, low vaccination rates rival those of developing countries such as South Sudan. Not surprisingly, these communities have also experienced whooping cough outbreaks. Low vaccination rates are also implicated as one of the reasons cases of measles are on the rise in California.

However, even with certain portions of the population choosing not to vaccinate, the overall rate of vaccination in the United States is quite high. For example, according to the CDC’s Morbidity and Mortality Weekly Report on August 29, 2014, in 2013, the national vaccination rate among children aged 1935 months was was higher than 90 percent for both the polio and MMR vaccines.Keeping immunization rates high is key to protecting a population from disease and illness, helping to ensure better health for a community as a whole.

More to Explore

History of Vaccines

Centers for Disease Control: Vaccines & Immunizations

Centers for Disease Control: Immunization Schedules

World Health Organization: Vaccines

Vaccines: Your Best Shot at Good Health

National Institute of Allergy and Infectious Diseases: Vaccine Research

Food and Drug Administration: Vaccines

U.S. Immunization Data

What Do You Think?