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There are five major types of vaccines and they are differentiated by what type of antigen is used. Live attenuated vaccines are created from the actual disease in question, however before injection the [[pathogen]] is [[attenuated]] (weakened) by growing successive generations of the pathogen in poor nutrient conditions. Because they contain live pathogens, it is still possible for these vaccines to cause infection, particularly in imunnocompromised individuals. Inactivated vaccines are created from pathogens that have been killed, usually with [[formaldehyde]]. Toxoid vaccines are created by using toxins produced by the pathogen, these toxins are exposed to heat and/or chemicals such as formaldehyde to inactivate the toxins, but [[antibodies]] that are produced to these deactivated toxins will also protect against the real toxin. Subunit vaccines use pieces of the pathogen in the vaccine. These pieces often consist of unique protein segments that stimulate the production of antibodies. Finally, conjugate vaccines protect against bacteria that are encapsulated in  polysaccharides (complex sugars), which disguise the bacteria, making it hard for the immune system to recognize them. Conjugate vaccines overcome this by attaching the sugar to a protein the does stimulate the immune systeme, thus triggering the immune system to react to the sugar in the future even if it is not accompanied by the protein.<ref>https://www.cdc.gov/vaccines/hcp/conversations/downloads/vacsafe-understand-color-office.pdf</ref>

There are five major types of vaccines and they are differentiated by what type of antigen is used. Live attenuated vaccines are created from the actual disease in question, however before injection the [[pathogen]] is [[attenuated]] (weakened) by growing successive generations of the pathogen in poor nutrient conditions. Because they contain live pathogens, it is still possible for these vaccines to cause infection, particularly in imunnocompromised individuals. Inactivated vaccines are created from pathogens that have been killed, usually with [[formaldehyde]]. Toxoid vaccines are created by using toxins produced by the pathogen, these toxins are exposed to heat and/or chemicals such as formaldehyde to inactivate the toxins, but [[antibodies]] that are produced to these deactivated toxins will also protect against the real toxin. Subunit vaccines use pieces of the pathogen in the vaccine. These pieces often consist of unique protein segments that stimulate the production of antibodies. Finally, conjugate vaccines protect against bacteria that are encapsulated in  polysaccharides (complex sugars), which disguise the bacteria, making it hard for the immune system to recognize them. Conjugate vaccines overcome this by attaching the sugar to a protein the does stimulate the immune systeme, thus triggering the immune system to react to the sugar in the future even if it is not accompanied by the protein.<ref>https://www.cdc.gov/vaccines/hcp/conversations/downloads/vacsafe-understand-color-office.pdf</ref>

Since the adoption of mass vaccination programs, many diseases have been curbed. [[Smallpox]], a deadly disease responsible for the deaths of millions, has been entirely eliminated through vaccination, excepting some strains maintained in labs for research or weapons purposes. Responsible for an estimated 300 to 500 million deaths worldwide in the 20th century, vaccination programs of the 19th and 20th century were effective at curbing the disease, and in 1979 the World Health Organization declared smallpox to be eradicated.{{cn}}

Since the adoption of mass vaccination programs, many diseases have been curbed. [[Smallpox]], a disease responsible for the deaths of millions, has been entirely eliminated through vaccination, excepting some strains maintained in labs for research purposes. Responsible for an estimated 300 to 500 million deaths worldwide in the 20th century, vaccination programs of the 19th and 20th century were effective at curbing the disease, and in 1979 the World Health Organization declared smallpox to be eradicated.<ref>https://www.cdc.gov/smallpox/history/history.html</ref>

[[Polio]], for example, killed over 3,000 people in the United States in 1952 [http://www.cdc.gov/nchs/data/vsus/VSUS_1952_2.pdf], and afflicted such noted persons as President [[Franklin Delano Roosevelt]], actor Alan Alda, and musician Itzak Perlman. When doctors began using a vaccine to fight polio, it practically eradicated the disease in the developed world.

Another disease that has been eliminated from the US is [[Polio]], which killed over 3,000 people in the United States in 1952 [http://www.cdc.gov/nchs/data/vsus/VSUS_1952_2.pdf], and afflicted such noted persons as President [[Franklin Delano Roosevelt]], actor Alan Alda, and musician Itzak Perlman. When doctors began using a vaccine to fight polio, it practically eradicated the disease in the developed world.

The incidence of other diseases such as [[measles]], [[diptheria]], and [[pertussis]] has decreased greatly since the invention of vaccines against these diseases.<ref>https://www.unicef.org/pon96/hevaccin.htm</ref>

The incidence of other diseases such as [[diphtheria]], [[pertussis]], and [[measles]], has decreased greatly since the invention of vaccines against these diseases.<ref>https://www.unicef.org/pon96/hevaccin.htm</ref>

Traditionally a few highly tested vaccines were mandatory for children to protect against deadly or severe diseases, such as [[smallpox]] and [[polio]]. In the 1990s, vaccine manufacturers began introducing and persuading states to require numerous additional vaccines for non-deadly and even sexually transmitted diseases. About one-third of the states have philosophical exemptions entitling parents to decline the vaccines; 48 out of 50 states have religious exemptions; all states have medical exemptions, but they are hardest to obtain.<ref>http://www.nvic.org/state-site/state-exemptions.htm</ref><ref>http://www.vaccinesafety.edu/cc-exem.htm</ref>

Traditionally a few highly tested vaccines were mandatory for children to protect against deadly or severe diseases, such as [[smallpox]] and [[polio]]. In the 1990s, vaccine manufacturers began introducing and persuading states to require numerous additional vaccines for non-deadly and even sexually transmitted diseases. About one-third of the states have philosophical exemptions entitling parents to decline the vaccines; 48 out of 50 states have religious exemptions; all states have medical exemptions, but they are hardest to obtain.<ref>http://www.nvic.org/state-site/state-exemptions.htm</ref><ref>http://www.vaccinesafety.edu/cc-exem.htm</ref>