Currently, two typhoid vaccines of demonstrated safety and efficacy are available on the international market:
- The oral vaccine based on the live, attenuated mutant strain of S. typhi Ty21a (Ty21a vaccine), is supplied in enteric coated capsules. In Australia and Europe, three tablets are given on days 1, 3, and 5; this series is repeated every year for individuals travelling from nonendemic to endemic countries, and every 3 years for individuals living in countries or areas at risk. In North America, four tablets are given on days 1, 3, 5, and 7 and revaccination is recommended only after 7 years (Canada) or 5 years (USA) for all, regardless of typhoid fever risk in the country or area of residence. The duration of protection following Ty21a immunization is not well defined and may vary with vaccine dose and possibly with subsequent exposures to S. typhi (natural booster).
- The injectable Vi capsular polysaccharide vaccine (ViCPS vaccine)
is given intramuscularly in a single dose. Protection is induced about
7 days after the injection. In countries or areas at risk, the protective
efficacy 1.5 years after vaccination is about 72%; after 3 years it is
about 50%. The vaccine is licensed for individuals aged >2 years. To
maintain protection, revaccination is recommended every 3 years.
A combined typhoid/hepatitis A vaccine is also available in some countries.
Contraindications and precautions
Both typhoid vaccines are safe and there are no contraindications to their use other than previous severe hypersensitivity reactions to vaccine components. Proguanil, mefloquine and antibiotics should be stopped from 3 days before until 3 days after the administration of Ty21a. These vaccines are not recommended for use in infant immunization programmes due to insufficient information on their efficacy in children under 2 years of age.
Typhoid fever vaccination may be offered to those travelling to destinations where the risk of typhoid fever is high, especially individuals staying in endemic areas for >1 month and/or in locations where antibiotic-resistant strains of S. typhi are prevalent.