LONDON -- The age children are vaccinated against typhoid should be reassessed because, contrary to accepted belief, children under 5 are just as likely as older people to become infected and suffer major symptoms, researchers say.
In a study published in this week's issue of The Lancet, a British medical journal, doctors from India reported that the incidence of the potentially fatal disease -- an intestinal infection caused by the salmonella typhi bacterium in food or water contaminated with feces or urine -- in fact peaked at the age of 3.
The severity of the disease, which mostly occurs in developing countries, was similar for children under 5, older children and adults in terms of the duration of fever and need for hospitalization, according to the study by Dr. Maharaj Bhan, a professor of pediatrics at the All India Institute of Medical Sciences in New Delhi.
In many Western countries, health authorities generally recommend vaccination against typhoid for people older than 5 or 6 who plan to visit countries where the risk is high. Experts say there are two effective vaccines, but one is not recommended for children under 6 and the other has not been tested in that age group.
Neither vaccine is used in public health programs in developing nations, the study said.
In the United States, the Centers for Disease Control and Prevention recommends vaccination against typhoid mostly for those who plan to visit areas where the risk is high, such as Latin America, Asia and Africa.
"The current view is based on anecdotal evidence that this is a disease that occurs infrequently in children under 5. Nobody has really studied this age group," said Dr. George Griffin, a professor of infectious diseases and medicine at St. George's Hospital Medical School in London, who was not connected with the study.
"This study has reached definitive findings in a large group of people in this area," he said. "You can't extrapolate it to other countries -- research in individual countries where it might be different must also be done -- but this is the first group to have investigated it in this way and it's excellent."
The researchers studied 7,159 people under 40 -- 1,126 of whom were under 5 -- living in 1,820 households in a poor neighborhood of New Delhi for a year.
They visited each person twice a week and took blood samples from those who had developed a fever since the last visit to see if anyone had been infected with typhoid. Those who had were promptly treated with drugs.
Sixty-three people got typhoid. Forty-four percent of those cases were in children under 5, even though that age group represented only 16 percent of the total number of people studied.
Nine people -- seven of them under 5 -- didn't recover after taking antibiotics for 10 days and had to go to the hospital.
"Our findings challenge the common view of typhoid fever as a disorder that affects mainly children of school age and adults," the study said. "These findings also contradict the current view that typhoid in children under 5 years is mild."
"We suggest that current strategies for vaccination against typhoid fever need urgent review," the researchers said.
The researchers suggested that vaccines suitable for younger children need to be developed and that children in high-risk places such as the Kalkaji neighborhood of New Delhi be immunized against typhoid at the same time they get their measles shots -- at about 9 months of age.
But in a separate commentary published in the journal, Griffin wrote that introducing new vaccines into the current schedule of child immunizations even in developed nations is extremely difficult, partly because of concern they might interfere with other shots.