High Effectiveness of Indian Typhoid Vaccine

In News

A new study published in The New England Journal of Medicine (NEJM) shows that of the three types of typhoid vaccines available for commercial use, the Indian-made Typbar TCV vaccine was found to be highly effective.

In-Detail

  • The vaccine Typbar TCV was developed by Bharat Biotech and it was found to have 81.6% efficacy in preventing typhoid fever at 12 months.
  • Among children aged between 9 and 16 years, a single dose of the vaccine is found to be highly effective.
  • Typbar TCV was already recommended by the Strategic Advisory Group of Experts on Immunization (SAGE) of the World Health Organisation (WHO) in 2017.
  • In January 2018, the vaccine was prequalified by WHO.

Typhoid Fever

  • The fever is caused by the highly contagious Salmonella Typhi bacteria.
  • Every year, around 11 million fall sick due to typhoid and 1,17,000 deaths due to the fever are reported.
  • The bacteria is spread through contaminated food and water.

Typbar TCV

  • The vaccine is a conjugate vaccine, that is the antigen in the vaccine is chemically linked to a carrier protein. In this case, it is a polysaccharide.
  • The vaccine was tested in Nepal.
  • For the study, two other vaccines – polysaccharide typhoid vaccine and live, weakened typhoid vaccine were tested.
  • These two have low efficacy than Typbar TCV.
  • They show only 6-70% efficacy compared to Typbar’s  82% efficacy.
  • Typbar has other advantages too, it can be given to babies as young as six months while the other two cannot be given to children below two years of age.
  • According to WHO-SAGE, a large proportion of severe typhoid fever is found among children aged below two years.

Multi-Drug Resistant

  • Typhoid bacteria can be treated using antibiotics.
  • But, over the years, the bacteria have acquired multi-drug resistance.
  • Such infections have been recorded across South Asia and India.
  • In Pakistan, since 2016, extensively drug-resistant (XDR) typhoid is being reported.
  • XDR is booming prevalent in India, Bangladesh, and Pakistan.
  • Hence the need for a vaccine.

The Trials

  • In a small phase-3 trial conducted in Nepal among two groups of people – 2-45 years old and 6-23 months, the vaccine was found to be provoking an immune response in 98% of the vaccinated children.
  • In phase-2b human challenge trials, healthy adults in the age group of 18-60 years without any prior typhoid infection were vaccinated first and then were exposed to the bacteria. The efficacy of the vaccine was 88%.

Export Potential

  • The vaccine is licensed in India and available for clinical use.
  • Already the conjugate vaccine is being exported to Pakistan and some 10 million vaccines have been sent to Pakistan.
  • Pakistan is the first country in the world to include the typhoid vaccine as part of its national immunisation programme.
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