A cheap typhoid vaccine that would be affordable for the poor in developing countries has proved highly effective in protecting pre-school children, an international health body said Thursday.
A study conducted in a slum district of the Indian city of Kolkata has also shown the Vi vaccine protects the unvaccinated neighbours of those treated, the Seoul-based International Vaccine Institute (IVI) said in a statement.
Typhoid fever remains a major threat in developing countries, the IVI said, killing between 216,000-600,000 people annually worldwide. It spreads through contaminated food and water or contact with those infected.
Safe and effective vaccines exist but are used mainly by wealthy travellers to developing countries rather than by poor residents.
The World Health Organisation has recommended the Vi vaccine in developing countries because it costs only about 50 cents and only a single dose is needed.
But doubts about its effectiveness for pre-school children and in conferring "herd protection" on the unvaccinated have limited its use, according to the IVI.
The Kolkata study, whose findings are published by the New England Journal of Medicine, showed it was 80 percent effective in preventing typhoid fever among children under the age of five.
It also showed the vaccine offered 44 percent protection among the unvaccinated who came in contact with the immunised children.
"The protection for children under the age of five years is important because this age group has been shown to be at high risk for typhoid fever in many areas where the disease is epidemic," IVI director-general John Clemens said in the statement.
The Kolkata study was conducted by the IVI and India's National Institute of Cholera and Enteric Diseases.