• In a 2017 randomized control trial in Malawi involving 28,130 children aged 9 months to 12 years, the efficacy and durability of a single-dose Vi-TT vaccine against Typhoid Fever were assessed.

• 14,069 children received the typhoid vaccine, while the remaining 14,061 children received the control meningococcal vaccine.

• The effectiveness of the vaccine was measured over different periods.

• Vaccine efficacy reduced over time by only 1·3% per year over four years with rates of approximately 83.4%, 80.7%, 80.1%, and 77.1% observed at 1, 2, 3, and 4 years post-vaccination, respectively.

• Efficacy was consistent across age groups, including children under 2 years.

• These findings support WHO recommendations for Vi-TT mass campaigns in typhoid-endemic areas, followed by routine introduction, emphasizing long-term protection and efficacy.

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