What to Know About Typhoid Vaccines

Typhoid vaccines are used to prevent typhoid fever in children and adults. Typhoid fever (simply referred to as typhoid) is an infectious disease caused by a bacteria called Salmonella typhi that can lead to high fever, diarrhea, vomiting, pneumonia, encephalitis (inflammation of the brain), and, in some cases, death.

The disease, commonly associated with poor hygiene and public sanitation, can be prevented with one of two vaccines:

• Typhim Vi, an inactivated vaccine made with killed S. typhi bacterium that is delivered by injection
• Vivotif, a live attenuated vaccine made with weakened S. typhi that is taken orally (by mouth)

The vaccines work by stimulating the production of immune cells called antibodies that "recognize" S. typhi and prevent it from establishing an infection.

Typhoid is a major global health concern with around 21 million new cases and over 150,000 deaths each year. While relatively rare in the United States, around 5,700 cases are diagnosed annually, usually involving travelers who have been to parts of the world where typhoid is endemic.

Uses

Typhoid vaccines are not uses for the routine immunization of people in the United States. Rather, they are indicated for use in specific populations, namely:

• Travelers to areas where a recognized risk of exposure to typhoid exists
• People who live with or have intimate contact with someone who has typhoid fever
• Workers in microbiology labs who handle S. typhi samples

Typhoid vaccination is not required for international travel but is recommended for those traveling to parts of Africa, Asia, Central America, and South America where there is a recognized risk of S. typhi exposure.

Neither of the two vaccines are inherently "better" than the other, and both offer only partial protection against typhoid fever.

Before Use

There are certain people in whom typhoid vaccines may cause harm and need to be avoided. Typhim Vi and Vivotif are both contraindicated for use in people who have a history of allergy to any components of the vaccine.

As a live vaccine, Vivotif poses possible health risks to people who are immunocompromised. These include people with HIV, organ transplant recipients, people undergoing chemotherapy, and children with primary immunodeficiency (PID).

Live vaccines have the potential to revert to their virulent state in immunocompromised people, causing the very diseases they are meant to prevent. Although this has not been established with Vivotif, it is still contraindicated for use in people with immunodeficiency as a precaution.

Dosage

The recommended dosage of typhoid vaccines varies by the vaccine type and age. The vaccines are supplied as follows:

• Typhim Vi: Either as a single-use prefilled syringe or a multi-dose vial.
• Vivotif: A blister pack of pink-and-white capsules.

Revaccination is recommended for international travelers who frequent endemic regions. For Typhim Vi, revaccination is recommended every 2 years. for Vivotif, revaccination may only be needed every 5 years.

How to Take and Store

Typhim Vi is administered by a healthcare professional. The injection is given either to the deltoid muscle of the shoulder or the upper part of the outer thigh (anterolateral thigh). To ensure ample protection, the injection should be given at least 2 weeks prior to departure to an endemic region.

Vivotif is self-administered and should be taken 1 hour before food with a cold or lukewarm drink. Failing to follow these dietary instructions can undermine if the effectiveness of the vaccine. The vaccination series should be completed at least 1 week before travel to an endemic region.

Vivotif capsules should not be stored at room temperature but rather refrigerated at temperatures between 35.6°F to 46.4° F (2° C to 8° C). Do not freeze.

Side Effects

Side effects can occur with both Typhim Vi and Vivotif, although most tend to be mild and resolve on their without treatment. Side effects are a bit more common with Typhim Vi, affecting as many as one in six users.

Severe reactions—including the potentially life-threatening whole-body allergy known as anaphylaxis—are rare with typhoid vaccines. In fact, a 2019 review of studies in the Journal of Allergy and Clinical Immunology reported no cases of anaphylaxis out of 164,483 doses of typhoid vaccine administered.

Warnings and Interactions

Vivotif should not be used in anyone who is sick with fever or has an acute gastrointestinal illness as doing so may only make symptoms worse. In such cases, it is best to wait until the illness resolves before pursuing the live vaccine.

Neither animal nor human studies have not been conducted to assess the safety of Typhim Vi or Vivotif during pregnancy. With that said, the vaccines are classified as Pregnancy Category C drugs, meaning that the benefits of the vaccines may outweigh the potential risks. Speak with your doctor if you are pregnant, breastfeeding, or planning to get pregnant to make a fully informed choice.

Certain drugs and treatments can interact with Typhim and Vivotif. These include immunosuppressants that blunt the overall immune response and may temper the production of defensive antibodies. These include:

• Biologic drugs like Humira (adalimumab) and Xeljanz (tofacitinib)
• Chemotherapy drugs
• Cyclosporine
• High-dose corticosteroids
• Methotrexate
• Radiation therapy

Vivotif can also interact with anti-malaria drugs like Aralen (chloroquine) and Larium (mefloquine), both of which can impair the effectiveness of the vaccine. The interaction appears to be mild, but inform your doctor if you are taking or planning to take anti-malaria drugs before starting Vivotif.

How to Choose

There are both pros and cons to Typhim Vi and Vivotif, and one may be better for some people than for others. If in doubt about which vaccine is right for you, speak with your doctor.