News Excerpt:

A phase-3 trial in children aged between nine months and 12 years carried out in Malawi, Africa, which is a typhoid fever-endemic setting, has shown that the efficacy of the Hyderabad-based Bharat Biotech’s conjugate typhoid toxoid vaccine - Typbar - lasts for at least four years.

More on the news:

• In 2019, there were an estimated 9·24 million typhoid cases and 1,10,000 deaths worldwide. 
• The majority of typhoid cases and deaths in 2019 occurred in South-East Asia and Africa.

Key highlights of the study:

• Healthy children aged nine months to 12 years were randomly assigned to receive either Bharat Biotech’s conjugate typhoid vaccine (intervention group) or meningococcal.
• In total, 28,130 children were recruited for the trial, and 14,069 children received the typhoid vaccine, while the remaining 14,061 children received the control vaccine (MenA).
• The vaccine's efficacy at the end of 4.3 years of median follow-up was 70·6% in children aged nine months to two years.
• But in children aged two to four years, the efficacy was higher at 79·6%, whereas the efficacy was 79·3% in children aged five-12 years.
• According to the paper, the “absolute risk reduction was 6·1 typhoid infections per 1,000 vaccinated children, corresponding to a number needed to vaccinate 163 to prevent one case of typhoid fever”.
• The estimated cumulative vaccine efficacy was found to be 83·4% after one year, 80·7% after two years, 80·1% after three years, 77·1% after four years, and 78·3% after 4·61 years (the longest follow-up observed) following vaccination.
• The study provides evidence that conjugated typhoid vaccine provides durable overall protection beyond 48 months after vaccination among children vaccinated between nine months and 12 years of age, with little decline in efficacy over time. 
• They estimated that vaccine efficacy reduced over time by only 1·3% per year over four years.
• As per the study, conjugated typhoid vaccine has shown to induce robust immune responses in individuals older than six months.
• Currently, there are two conjugated typhoid vaccines —
• The Typbar TCV typhoid vaccine manufactured by Bharat Biotech which received WHO prequalification in 2017, 
• Biological E’s Vi-CRM197 conjugated typhoid vaccine, which received WHO prequalification in 2020.

About Typhoid:

• Typhoid fever is a bacterial infection that can spread throughout the body, affecting many organs.
• It's caused by a bacterium called Salmonella typhi, which is related to the bacteria that cause salmonella food poisoning.
• Typhoid fever is highly contagious. An infected person can pass the bacteria out of their body in their poo or, less commonly, in their pee.
• Typhoid fever is most common in parts of the world that have poor sanitation and limited access to clean water.
• Worldwide, children are thought to be most at risk of developing typhoid fever. This may be because their immune system (the body's natural defence against infection and illness) is still developing.
  • But children with typhoid fever tend to have milder symptoms than adults.
• Symptoms of typhoid fever:
  • A persistent high temperature that gradually increases each day
  • Headache
  • General aches and pains
  • Extreme tiredness (fatigue)
  • Cough
  • Constipation