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.