A BACTERIUM called Salmonella typhi travels from host to host in contaminated food and water. Thanks to better mains and drains its excursions have been curtailed in rich countries. But the disease that it causes—typhoid fever—is still common in places where modernity has not fully made its mark. In these parts between 11m and 20m people fall ill with typhoid every year. Of those 160,000, mostly children, die.
Typhoid fever can be treated with antibiotics, but this line of defence is starting to fail as extensively drug-resistant (XDR) bugs are spreading rapidly and alarmingly in Pakistan. Existing vaccines provide only temporary protection to adults and do not work in children. What is needed is a new and better vaccine. And one is now at hand, courtesy of the Bill and Melinda Gates Foundation, a big charity.
The origins of this vaccine, which labours under the moniker of Typbar-TCV, can be traced back to work done 20 years ago by researchers at America’s National Institutes of Health. It was only ever licensed to Bharat Biotech, based in Hyderabad, India, for local use. Nobody else thought it worthwhile developing. Now the Gates Foundation has plucked Typbar-TCV from obscurity and pushed it through the research and testing necessary for it to be used everywhere.
One of the first of those tests was conducted by the Oxford Vaccine Group (OVG), a research organisation in Britain, in 2017. Andrew Pollard, OVG’s boss, recruited 100 adult volunteers, vaccinated them and then gave them a drink laced with live S. typhi. Britain was a good place to do this because typhoid is essentially extinct there, so participants had no existing immunity. Antibiotics were on hand to treat those who succumbed, but most did not. This and subsequent experiments have shown the vaccine to be almost 90% effective and, crucially, safe for use in children as young as six months.
Fever pitch
The Gates Foundation has just sent a supply of 200,000 doses of Typbar-TCV to Pakistan, to try and fight the outbreak of XDR typhoid there. In Sindh province (mostly in the capital, Karachi), there were 5,274 cases of XDR typhoid (of 8,188 cases overall) between November 1st 2016 and December 9th last year.
The new vaccine has also been warmly welcomed by GAVI, an international health organisation formerly known as the Global Alliance for Vaccines and Immunisation, which has promised to spend $85m on Typbar-TCV this year and next. GAVI was supposed to start vaccinations in Zimbabwe this week. The doses are already in the country. However, according to Seth Berkley, GAVI’s boss, strikes, protests and a deteriorating security situation have meant that the beginning of the campaign has been postponed until February 23rd.
Other places where the vaccine could be deployed include Bangladesh, Ghana, India, Nepal, Nigeria and Uganda. Besides being able to bring typhoid outbreaks in countries like these to a halt, vaccination may also help drive down the use of antibiotics, and thus the selection pressure that maintains XDR bacteria in the population. Anita Zaidi, head of the vaccine-development, surveillance, and enteric and diarrhoeal diseases programmes at the Gates Foundation, even wonders if it might be possible to eliminate typhoid entirely if enough people are vaccinated.
That is an aspiration. Typbar-TCV does, though, bring the immediate hope of saving many lives. What a shame it has arrived 20 years later than it might have done.
—
This article appeared in the Science and Technology section of the print edition of The Economist under the headline “Better late than never”.
Source: Economist.com
