Typhoid vaccine explained

Typhoid vaccine should not be confused with typhus vaccine.

Typhoid vaccines are vaccines that prevent typhoid fever.[1] [2] [3] Several types are widely available: typhoid conjugate vaccine (TCV), Ty21a (a live oral vaccine) and Vi capsular polysaccharide vaccine (ViPS) (an injectable subunit vaccine). They are about 30 to 70% effective in the first two years, depending on the specific vaccine in question. The Vi-rEPA vaccine has been shown to be efficacious in children.[4]

The World Health Organization (WHO) recommends vaccinating all children in areas where the disease is common.[1] Otherwise they recommend vaccinating those at high risk.[1] Vaccination campaigns can also be used to control outbreaks of disease.[1] Depending on the vaccine, additional doses are recommended every three to seven years.[1] In the United States the vaccine is only recommended in those at high risk such as travelers to areas of the world where the disease is common.[5]

The vaccines available as of 2018 are very safe.[1] Minor side effects may occur at the site of injection.[1] The injectable vaccine is safe in people with HIV/AIDS and the oral vaccine can be used as long as symptoms are not present.[1] While it has not been studied during pregnancy, the non-live vaccines are believed to be safe while the live vaccine is not recommended.[1]

The first typhoid vaccines were developed in 1896 by Almroth Edward Wright, Richard Pfeiffer, and Wilhelm Kolle.[6] Due to side-effects newer formulations are recommended as of 2018.[1] It is on the World Health Organization's List of Essential Medicines.[7] [8]

Medical uses

Ty21a, the Vi capsular polysaccharide vaccine, and Vi-rEPA are effective in reducing typhoid fever with low rates of adverse effects.[4] Newer vaccines such as Vi-TT (PedaTyph) are awaiting field trials to demonstrate efficacy against natural exposure.[4]

The oral Ty21a vaccine prevents around one-half of typhoid cases in the first three years after vaccination. The injectable Vi polysaccharide vaccine prevented about two-thirds of typhoid cases in the first year and had a cumulative efficacy of 55% by the third year. The efficacy of these vaccines has only been demonstrated in children older than two years.[4] Vi-rEPA vaccine, a new conjugate form of the injectable Vi vaccine, may be more effective and prevents the disease in many children under the age of five years.[9] In a trial in 2-to-5-year-old children in Vietnam, the vaccine had more than 90 percent efficacy in the first year and protection lasted at least four years.[10]

Schedule

Depending on the formulation it can be given starting at the age of two (ViPS), six (Ty21a), or six months (TCV).[1]

Types

Notes and References

  1. ((World Health Organization)). 2018. Typhoid vaccines: WHO position paper – March 2018. Weekly Epidemiological Record. 93. 13. 153–172 . 10665/272273 . World Health Organization .
  2. Web site: Summary of the WHO Position Paper on Typhoid vaccines: WHO position paper – March 2018 . origin.who.int . October 23, 2019 . https://web.archive.org/web/20191023041242/http://origin.who.int/immunization/policy/position_papers/PP_typhoid_2018_summary.pdf . October 23, 2019 . dead.
  3. ((World Health Organization)) . Typhoid vaccines: WHO position paper, March 2018 - Recommendations . Vaccine . 37 . 2 . 214–216 . 2019 . 29661581 . 10.1016/j.vaccine.2018.04.022 . 4902671 .
  4. Milligan R, Paul M, Richardson M, Neuberger A . Vaccines for preventing typhoid fever . The Cochrane Database of Systematic Reviews . 2018 . CD001261 . May 2018 . 5 . 29851031 . 6494485 . 10.1002/14651858.CD001261.pub4 .
  5. Web site: Typhoid Vaccine Information Statement . U.S. Centers for Disease Control and Prevention (CDC) . 15 December 2015. October 2019 . live. https://web.archive.org/web/20151208185803/http://www.cdc.gov/vaccines/hcp/vis/vis-statements/typhoid.html. 8 December 2015.
  6. Book: Flower DR . Bioinformatics for Vaccinology.. 2008. John Wiley & Sons. Chichester. 9780470699829. 40–41. live. https://web.archive.org/web/20151222095533/https://books.google.com/books?id=Rg6-T_1-LWkC&pg=PA40. 22 December 2015.
  7. Book: ((World Health Organization)) . World Health Organization model list of essential medicines: 21st list 2019 . 2019 . 10665/325771 . World Health Organization . World Health Organization . Geneva . WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO . free .
  8. Book: ((World Health Organization)) . World Health Organization model list of essential medicines: 22nd list (2021) . 2021 . 10665/345533 . World Health Organization . World Health Organization . Geneva . WHO/MHP/HPS/EML/2021.02 . free .
  9. Lin FY, Ho VA, Khiem HB, Trach DD, Bay PV, Thanh TC, Kossaczka Z, Bryla DA, Shiloach J, Robbins JB, Schneerson R, Szu SC . The efficacy of a Salmonella typhi Vi conjugate vaccine in two-to-five-year-old children . The New England Journal of Medicine . 344 . 17 . 1263–9 . April 2001 . 11320385 . 10.1056/nejm200104263441701 . free .
  10. Szu SC . Development of Vi conjugate - a new generation of typhoid vaccine . Expert Review of Vaccines . 12 . 11 . 1273–86 . November 2013 . 24156285 . 10.1586/14760584.2013.845529 . 23280555 .
  11. Web site: Typhim Vi . U.S. Food and Drug Administration (FDA) . 22 July 2017 . 29 December 2019.
  12. Web site: Vivotif . U.S. Food and Drug Administration (FDA) . 1 February 2018 . 29 December 2019.
  13. Web site: Typhoid vaccine prequalified. https://web.archive.org/web/20180104014508/http://www.who.int/medicines/news/2017/WHOprequalifies-breakthrough-typhoid-vaccine/en/. dead. 4 January 2018. 3 January 2018. 9 December 2019. who.int.

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