Indians develop long-lasting typhoid vaccine

In what has been described as a great leap in vaccine research, scientists here have identified a long-lasting candidate vaccine against typhoid, which kills thousands in several developing countries including India.

Developed by National Institute of Cholera and Enteric Disease (NICED) and patented by its parent body Indian Council of Medical Research (ICMR), the vaccine is expected to eliminate periodic inoculation to protect people from typhoid.

“Even though we do not know exactly how long our vaccine will protect without human trials, it is a protein vaccine and usually protein vaccines give 5-10 years of protection,” Santasabuj Das, a NICED scientist who led the typhoid vaccine initiative told Deccan Herald.

The vaccine is based on a viral protein, T2544 identified by Das and his colleagues, who reported the vaccine candidate in the Proceedings of the National Academy of Sciences in February. The bug uses this protein to latch on to victims' cells. Studies using typhoid patients' blood samples and mice experiments show that the NICED vaccine is safe and twice as effective as Typherix, a single-shot vaccine available in the market at a cost of Rs 500. Typherix gives 80 per cent protection up to one year and 60 per cent protection after two years in kids. But a repeat shot is needed after three years to maintain the protective cover. Typhoid causes an estimated 26 million infections each year with more than 200,000 deaths. The number of cases is particularly high in parts of South Asia including India where the prevalence range from 102 to 2219 per 100,000 population.

Characterised by high fever and diarrhoea, the disease is transmitted through the ingestion of food or drink contaminated by the faeces or urine of infected people.
 Though there are drugs for treatment, detection of the disease in time still remains a big challenge for doctors.

The two bugs that cause the disease in India – Salmonella typhi and Salmonella paratyphi – have developed resistance to many antibiotics over the years. Sometimes, the infection can remain in the patient’s gall bladder after being cured cure, triggering cancer.

Lack of long-term protection has remained a key reason for the vaccines not picking up, despite World Health Organisation (WHO) recommendation for vaccines since the early 1980s.  “Typhoid vaccine is advisable even if it has to be re-administered after three years. Typhoid seems to have lost its seasonality and now one sees cases of this disease, all the year through,” said Sandeep Budhiraja, a doctor from Max Healthcare, a private hospital in Delhi. However, most doctors still prefer typhoid vaccine as a secondary option and not as important as the first line vaccines.

ICMR is on the look out for an industrial partner to further develop the crude vaccine and take up clinical trials.