What is Vivaxim (combined hepatitis A and typhoid vaccine)?

Vivaxim: Combined Hepatitis A and Typhoid Vaccine

Vivaxim is a combined inactivated vaccine containing hepatitis A antigen (160 ELISA units of AVAXIM) and typhoid Vi polysaccharide (25 micrograms) in a single 1 mL intramuscular injection, licensed for use in travelers aged 16 years and older requiring protection against both diseases. 1, 2

Vaccine Composition and Formulation

• The vaccine contains inactivated hepatitis A virus antigen (AVAXIM component) combined with purified Vi capsular polysaccharide from Salmonella typhi (Typhim Vi component) in a dual-chamber presentation 1, 3
• The formulation delivers both antigens simultaneously, eliminating the need for two separate injections when protection against both hepatitis A and typhoid fever is indicated 4

Immunogenicity and Efficacy

Vivaxim demonstrates excellent immunogenicity for both components, with >95% of recipients achieving protective anti-Vi antibodies and >86% achieving protective anti-hepatitis A antibodies within 14 days of vaccination. 4

• At one month post-vaccination, seroconversion rates exceed 94% for both antigens, with geometric mean titers comparable to monovalent vaccines administered separately 4, 5
• The hepatitis A component provides long-term protection consistent with other inactivated hepatitis A vaccines, achieving seroprotection rates of 99% at 3 years when used as part of a prime-boost strategy 1
• The typhoid component offers protection comparable to standalone Vi polysaccharide vaccines, though boosters are required every 2-3 years for continued protection 6, 7

Licensed Indications and Target Population

• Vivaxim is officially licensed for travelers aged 16 years and older who require simultaneous protection against hepatitis A and typhoid fever 2
• The vaccine is particularly indicated for travelers to endemic regions in Latin America, Asia, and Africa where both diseases are prevalent 6, 7
• Additional indications include laboratory workers handling Salmonella typhi and household contacts of documented typhoid carriers who also require hepatitis A protection 6

Off-Label Use in Children

Despite licensure only for ages 16 and older, Vivaxim has been widely used off-label in children aged 2-16 years, with observational data demonstrating good tolerability and safety in this age group. 2

• A prospective study of 425 children aged 2-16 years showed no serious adverse events, with 26.8% experiencing no side effects at all 2
• Local reactions (sore arm 70.5%, redness 16%, swelling 11.1%) were more common than with monovalent vaccines, likely due to the larger injection volume 2
• Systemic reactions remained mild, with tiredness (5.9%), headache (4.2%), and fever (3.4%) being most common, and less than 5% of children missing school or activities 2

Administration and Dosing

• The vaccine is administered as a single 1 mL intramuscular injection into the deltoid muscle 1, 4
• For hepatitis A protection, a booster dose is required 6-12 months after the initial dose, which can be given as either Vivaxim again or monovalent hepatitis A vaccine 3
• For typhoid protection, boosters are recommended every 2-3 years under conditions of continued exposure 6, 7

Safety Profile and Adverse Events

Vivaxim demonstrates an excellent safety profile with predominantly mild, self-limited adverse events and no serious adverse events reported in clinical trials. 2, 4, 5

• Pain at the injection site is the most frequent local symptom, occurring in approximately 70% of recipients but typically mild and transient 2, 4
• Headache is the most common systemic symptom, reported in less than 5% of recipients 4
• Local reactions are approximately twice as frequent compared to monovalent vaccines, attributed to the larger 1 mL injection volume versus 0.5 mL for single-antigen vaccines 3
• All reported symptoms resolve without sequelae, and the vaccine can be safely administered with other travel vaccines 5, 8

Simultaneous Administration with Other Vaccines

• Vivaxim can be administered simultaneously with other inactivated vaccines without affecting immunogenicity or increasing adverse events 1
• The hepatitis A component does not interfere with typhoid, diphtheria, tetanus, poliovirus, Japanese encephalitis, rabies, or yellow fever vaccines when given concomitantly 1
• When multiple vaccines are given on the same day, they should be administered at different injection sites 2

Clinical Advantages

The primary advantage of Vivaxim is improved compliance and convenience by reducing the number of injections required for travelers needing protection against both diseases. 4, 8

• Single-injection administration improves vaccine coverage and adherence, particularly important for last-minute travelers 4
• The vaccine provides rapid seroconversion, with protective antibody levels achieved within 2 weeks for most recipients 4
• Cost-effectiveness is enhanced by combining two vaccines into a single clinic visit 8

Important Limitations and Caveats

• Vivaxim does not provide 100% protection against either disease and should not replace careful food and water precautions during travel 6, 7
• The vaccine is contraindicated in individuals with severe hypersensitivity to any vaccine component 1
• Immunocompromised individuals may have reduced immune responses and should be counseled accordingly 6
• The typhoid component requires more frequent boosting (every 2-3 years) compared to newer typhoid conjugate vaccines which offer longer protection 6, 9