Ty21a
{{Short description|Typhoid vaccine}}
{{Infobox drug
| verifiedrevid = 449938078
| image = Vivotif-typhoid-live-oral-vaccine.JPG
| type = vaccine
| target = Typhoid
| vaccine_type = attenuated
| tradename = Vivotif
| pregnancy_AU =
| pregnancy_US = B
| pregnancy_category =
| legal_AU = S4
| legal_CA = Unscheduled
| legal_UK = POM
| legal_US = Rx-only
| legal_status =
| routes_of_administration = Oral
| CAS_number_Ref = {{cascite|correct|??}}
| CAS_number = 1704529-13-4
| ATC_prefix = J07
| ATC_suffix = AP01
| PubChem =
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank =
}}
Ty21a is a live attenuated bacterial vaccine that protects against typhoid. First licensed in Europe in 1983 and in the United States in 1989, it is an orally administered, live-attenuated Ty2 strain of S. Typhi in which multiple genes,
including the genes responsible for the production of Vi, have been deleted so as to render it harmless but nevertheless immunogenic. It is one of the three typhoid vaccines currently recommended by the World Health Organization (the other two being the Typhoid Conjugate Vaccine (TCV) and Vi capsular polysaccharide vaccine).{{Cite web |url= https://www.who.int/immunization/policy/position_papers/PP_typhoid_2018_summary.pdf |title=WHO position paper on typhoid Vaccines, March 2018|date=March 2018|website=World Health Organization|access-date=2019-05-05}}
The vaccine is given by mouth. The vaccine is presented either as enteric coated capsules or as a liquid suspension. The vaccine must be stored at 2 to 8 °C, but will retain its potency for 14 days at 25 °C.{{cite journal | vauthors = ((World Health Organization)) | title = Typhoid vaccines: WHO position paper | journal = Relevé Épidémiologique Hebdomadaire | volume = 83 | issue = 6 | pages = 49–59 | date = February 2008 | pmid = 18260212 | url = https://www.who.int/wer/2008/wer8306.pdf }}
Medical uses
The vaccine offers a statistically significant protection for the first seven years.{{cite journal | vauthors = Milligan R, Paul M, Richardson M, Neuberger A | title = Vaccines for preventing typhoid fever | journal = The Cochrane Database of Systematic Reviews | volume = 2018 | issue = 5 | pages = CD001261 | date = May 2018 | pmid = 29851031 | pmc = 6494485 | doi = 10.1002/14651858.CD001261.pub4 }} The vaccine is most commonly used to protect travelers to endemic countries, but some agencies claim that the vaccine could be used in large scale public prevention programs.
The Vi polysaccharide vaccine is also effective at preventing typhoid fever.
Dosing
The recommended dose varies according to country and preparation. At least three doses are required for protection.{{Cite web|url=https://www.who.int/vaccine_safety/initiative/tools/Typhoid_vaccine_rates_information_sheet.pdf|title=World Health Organization Information sheet: Observed rate of vaccine reactions- Typhoid Vaccine|date=April 2014|website=WHO}}
In the US and Canada, an initial course of 4 doses on alternate days is recommended. Full protection is achieved 7 days after the last dose. In the US, a booster dose is recommended after 5 years. In Canada, a booster dose is recommended after 7 years.{{citation needed|date=September 2022}}
In Australia and Europe, an initial course of 3 doses on alternate days is recommended. Protection is achieved 7 days after the last dose. A booster dose is recommended every 3 years for people living in endemic areas, but every year for people traveling from non-endemic to endemic areas.{{cite book | vauthors = Salisbury D, Ramsay M, Noakes K | publisher = Department of Health | title = Immunisation against infectious disease | chapter = "Chapter 33: Typhoid" | chapter-url = http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_125348.pdf | page = 418 | isbn = 0-11-322528-8 | date = 2006-12-11 }}{{Dead link|date=January 2025 |bot=InternetArchiveBot |fix-attempted=yes }}
Side effects
Trade names
Research
Ty21a may also provide some degree of protection against paratyphoid fever A and B.{{cite journal | vauthors = Levine MM, Ferreccio C, Black RE, Lagos R, San Martin O, Blackwelder WC | title = Ty21a live oral typhoid vaccine and prevention of paratyphoid fever caused by Salmonella enterica Serovar Paratyphi B | journal = Clinical Infectious Diseases | volume = 45 | pages = S24–S28 | date = July 2007 | issue = Suppl 1 | pmid = 17582564 | doi = 10.1086/518141 | doi-access = free }} This cross-protection by a typhoid vaccine is most likely due to O antigens shared between different S. enterica serotypes.{{cite journal | vauthors = Whitaker JA, Franco-Paredes C, del Rio C, Edupuganti S | title = Rethinking typhoid fever vaccines: implications for travelers and people living in highly endemic areas | journal = Journal of Travel Medicine | volume = 16 | issue = 1 | pages = 46–52 | year = 2009 | pmid = 19192128 | doi = 10.1111/j.1708-8305.2008.00273.x | doi-access = free }}
A newer Vi-rEPA vaccine is being tested for preventing typhoid fever. It has a similar level of protection, but the protection may last longer with this newer vaccine.
References
{{reflist}}
External links
- [http://www.paxvax.com/typhoid-vivotif Manufacturer's Product Page] {{Webarchive|url=https://web.archive.org/web/20170612003031/http://www.paxvax.com/typhoid-vivotif |date=2017-06-12 }}
{{Vaccines}}
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