Sunday, February 26, 2012

Diseases eliminated from the U.S. by vaccines


I'm still working on my pertussis vaccine post. I'm also preparing to give a presentation this week, so I decided to use the material for that presentation for a post here.

You may have heard about disease eradication. So far, smallpox is the only disease to have been eradicated. Guinea worm (not a vaccine-preventable disease) and polio eradication programs are ongoing.

Eradication means that the disease no longer occurs anywhere in the world. Smallpox was declared eradicated in 1980. Once a disease has been eradicated, there is no longer a need for control measures. Smallpox vaccines are no longer recommended for the general population. I was born before the beginning of the smallpox eradication program, so I have a smallpox vaccination scar; Holly, who was born after smallpox vaccination in the U.S. was stopped, does not.

Elimination means that a disease no longer occurs within a geographic area. Because there is a risk for the disease to be imported from an area where the disease still occurs, control measures must continue. Importation occurs when a person is infected with a pathogen (a disease-causing bacteria, virus, fungus, or parasite) in an area where that disease still occurs and then enters a country where the disease does not occur.

  • Prior to the introduction of the vaccine, there were more than 125,000 cases of diphtheria and 10,000 deaths from diphtheria every year in the U.S.
  • Diphtheria was the leading cause of childhood death in Canada from 1921 to 1924
  • The last outbreak of diphtheria in the U.S. was in Seattle, Washington from 1972 to 1982
  • There has not been a case of diphtheria in the U.S. since 2003
  • Outbreaks continue to occur in Africa, Eastern Europe, Latin America and Southeast Asia
  • Cases of diphtheria have been imported to the U.S.
Measles
  • Prior to the introduction of measles, there were 200,000 to 500,000 cases of measles in the U.S. every year
  • Measles vaccine was license in the U.S. in 1963
  • Thirty seven years later, measles was declared eliminated from the U.S.
  • Outbreaks of measles continue to occur in countries where measles vaccination coverage is low
  • Worldwide, there were 164,000 deaths from measles in 2008; down from 2.6 million in 1980
  • Last year, there was a measles epidemic in Europe and cases of measles were imported by U.S. citizens traveling abroad

Improvements in sanitation have generally resulted in reduction in communicable diseases. Paradoxically, improved sanitation resulted in polio epidemics. Polio had been a common infection in babies who were partially protected by maternal antibodies (passive immunity). The infection was usually mild or inapparent. With improved hygiene standards, polio became an infection of older children who were no longer protected by maternal antibodies.
  • In 1952 there were 57,628 cases of polio in the U.S.
  • The "Salk" (inactivated injected) polio vaccine was licensed in 1955
  • The "Sabin" (live oral) polio vaccine was licensed in 1960
  • Polio was declared eliminated from the U.S. in 1979.

Rubella and congential rubella syndrome were the topic of one of my previous posts.
  • Rubella vaccine was first license in the U.S. in 1969
  • Rubella and congenital rubella syndrome were declared eliminated from the U.S. in 2004
  • The same year, 9 cases of rubella and 4 cases of congenital rubella syndrome were imported to New Hampshire

It's important to remember why we vaccinate. Many people in this country, including doctors and nurses, have never seen these diseases. I saw measles when I worked in Ethiopia, and we conducted acute flaccid paralysis (AFP) surveillance for polio while I was there. I had a great aunt who, as the result of a childhood polio infection, spent most of her life in a wheelchair.

It's easy to forget how serious these diseases are. When immunization rates are high and the incidences of vaccine-preventable diseases are low, the side effects of vaccines become more apparent than the diseases they prevent, and people can begin to question the benefit of vaccines (See: Life cycle of an immunization program).

References

Centers for Disease Control and Prevention. (2005). Imported cases of congential rubella syndrome – New Hampshire, 2005. Morbidity and Mortality Weekly Report, 54(45), 1160-1161. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5445a5.htm.

Centers for Disease Control and Prevention. (2011). Diphtheria. In Manual for the surveillance of vaccine-preventable diseases (5th Ed.). http://www.cdc.gov/vaccines/pubs/surv-manual/chpt01-dip.html.

Centers for Disease Control and Prevention. (2011). Measles imported by returning U.S. travelers aged 6-23 months, 2001-2011. Morbidity and Mortality Weekly Report, 60(13), 397-400. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6013a1.htm?s_cid=mm6013a1_w.

Dowdle W. R. (1998). The principles of disease elimination and eradication. Morbidity and Mortality Weekly Report, 48(SU01), 23-27. http://www.cdc.gov/mmwr/preview/mmwrhtml/su48a7.htm.

Gerson, A. A. (2009). Measles virus (rubeola). In Mandell, G. L., Bennett, J. E., & Dolin, R. (Eds.). Mandell, Douglas, and Bennett’s principles and practice of infectious diseases. (7th Ed.) [Electronic version].

MacGregor, R. R. (2009). Corynebacterium diphtheria. In G. L. Mandell, J. E. Bennett, & R. Dolin (Eds.), Mandell, Douglas, and Bennett's principles and practice of infectious diseases (7th ed.). [Electronic version].

Malonado, Y. A. (2009). Polioviruses. In S. S. Long (Ed.) Principles and practice of pediatric infectious diseases (3rd Ed.) [Electronic version].

Modlin, J. F. (2009). Poliovirus. In Mandell, G. L., Bennett, J. E., & Dolin, R. (Eds.). Mandell, Douglas, and Bennett’s principles and practice of infectious diseases. (7th Ed.) [Electronic version]

Overturf, G. D. (2009). Corynebacterium diphtheriae. In S. S. Long (Ed.) Principles and practice of pediatric infectious diseases (3rd ed.). [Electronic version]. Philadelphia: Elsevier.

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