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 The test in Nepal "provides the first evidence of the level of
impact and the potential for improving the health of children in
some of these very vulnerable populations around the world," lead
author Andrew Pollard of Oxford University in the UK told Reuters
Health in a telephone interview.
Preventing typhoid has become particularly important because some
strains, particularly in South Asia, are becoming resistant to
antibiotics. Pakistan is currently in the midst of an
antibiotic-resistant typhoid outbreak.
There are two existing typhoid vaccines. One comes in a capsule that
is too large for younger children to swallow, so it is for
youngsters over age 6. The other, delivered as an injection, doesn't
work in children under age 2.
As a result, people from Western countries who have young children
and travel to parts of the world where typhoid is a threat have to
be particularly vigilant to make sure their children drink water
that is properly boiled or filtered, and their food is properly
prepared, Pollard said.
The new test, reported in the New England Journal of Medicine,
involved children as young as 9 months. They will be followed for
another year in an attempt to determine how long the vaccine
protects against typhoid, a bacterial infection often spread through
contaminated water in regions of the world with poor sanitation.
Untreated, the disease can leave people sick for weeks or months.
Children are particularly vulnerable.
Further two-year field tests are also underway in Bangladesh and
Africa to gauge its effectiveness there.
The vaccine, known as TCV, has already been endorsed by the World
Health Organization's Global Advisory Committee on Vaccine Safety
based in part on earlier tests at Oxford "where we vaccinated people
and deliberately infected them with typhoid by asking them to drink
typhoid in a bicarbonate solution. That demonstrated that the
vaccine was protective," said Pollard.
The results from Nepal show the vaccine can work in a setting where
typhoid is common.
"I would call this new study more of an implementation and impact
study," he said. "These new studies are about providing confidence
in the field about the way the vaccine could be introduced in
vaccinating everyone from 9 months to 15 years of age, and it's
showing this huge impact."
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The TCV, or typhoid conjugate vaccine, was developed by Bharat
Biotech International of Hyderabad, India. Except for donating some
of the vaccine, sold under the brand name Typbar-TCV, Bharat was not
involved in the test.
The vaccine was given to 10,005 children in Lalitpur, Nepal, where
the disease is endemic. Another 10,014 were immunized against
meningococcal disease (MenA) to serve as a control group. One dose
was given. It took about a month for the vaccine to provide
protection.
Potential cases of typhoid were identified among children who were
reported to have a fever lasting at least two days during a visit to
Patan Hospital or one of 18 clinics. Blood cultures were used to
confirm the infection. Telephone calls at three-month intervals were
used to identify additional cases and vaccination side effects.
While 38 children given meningococcal conjugate vaccine developed
typhoid fever, there were only 7 cases among the youngsters given
the TCV.
Reported adverse events were similar in both groups and the rate of
vaccine-related fever within the first week after treatment was
about 5% in both groups.
The researchers chose the lower age limit of 9 months to coincide
with the time when babies get their measles vaccinations.
The test was conducted by the Baltimore, Maryland-based Typhoid
Vaccine Acceleration Consortium, a partnership between Oxford, the
University of Maryland School of Medicine and the international
nonprofit organization PATH.
SOURCE: https://bit.ly/2Dt7mGt The New England Journal of Medicine,
online December 4, 2019.
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