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.
- 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.
- 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.
- 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.
- 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.
- 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%.
- 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.