Friday, February 9, 2018

Routine childhood immunizations could include typhoid vaccine

By Esther Nakkazi

The World Health Organization (WHO) has prequalified a typhoid vaccine that can be administered to children as young as six months of age and included with other routine childhood immunizations.

The WHO announced the prequalification Typbar-TCV, - a type of vaccine that is created by joining an antigen to protein molecule ̶ early this month (3 January), making it the first vaccine approved by WHO to be given to children under the age of two who are disproportionately impacted by typhoid.

According to International Health Metrics and Evaluation (IHME) estimates that in 2016, there were about 12 million cases of typhoid fever resulting in around 130,000 deaths.

The IHME says currently a third of the global population is at risk of typhoid fever, which results in reduced school attendance, loss of work and wages, lowered pregnancy outcomes and impaired the physical and cognitive development of children.

Typhoid fever is caused by the bacterium Salmonella Typhi (S. Typhi), which infects humans due to contaminated food and beverages from sewage and other infected humans.

“The WHO’s decision to prequalify Typbar-TCV is a key step in expanding access to life-saving typhoid conjugate vaccines,” said Kathy Neuzil, director of the Center for Vaccine Development at the University of Maryland School of Medicine.

Krishna Ella, chairman and managing director of Bharat Biotech, which developed the prequalified vaccine, says that clinical trials have shown that t giving the vaccine at 25 micrograms per dose has proven longterm protection for children and adults, and can be administered to children from 6 months of age.

Tabley Bakyayita, an acting assistant commissioner health services at the Uganda Ministry of Health, tells Uganda ScieGirl that the WHO prequalification of Typbar-TCV could make the vaccine available more widely as it indicates that it meets international standards and serves as an endorsement of quality, efficacy, and safety.

Typbar-TCV is a Vi-tetanus toxoid conjugate vaccine manufactured by the Indian company Bharat Biotech and is delivered through intramuscular injection and offers advantages over currently available typhoid vaccines. For instance, one injectable typhoid conjugate vaccine (TCV) of longer and higher levels of immunogenicity compared with the injectable Vi polysaccharide (ViPS) vaccine.

A single 0.5 mL dose offers protection for at least 3 years to adults, children, and infants over 6 months of age was recently recommended by WHO’s Strategic Advisory Group of Experts (SAGE) on Immunization but recommended further studies to determine the need for a booster dose.

“Countries can now begin applying for funding assistance from Gavi, the Vaccine Alliance, to support the introduction of Typbar-TCV,” said Neuzil.

Bharat Biotech additionally announced a further price reduction to $1.00 or below per dose for low-income countries after the procurement of 100 million doses.

But Bakyayita said Uganda is not yet ready to include it in routine immunization services because the disease burden is not big enough to justify the introduction of a typhoid vaccine to be administered routinely.

It is also not cost effective and there is no evidence of antibiotic-resistant Salmonella Typii in the country or at least the surveillance system has not captured it, said Bakyayita.

However, private practitioners can have it and provide it like they have done so with other vaccines which are not given by the government routinely like Rota vaccine, yellow fever, Meningitis and others said Bakyayita.

A pediatrician who did not want to be named said Uganda may for now not need the typhoid vaccine for children but toilets and better sanitation.

The SAGE committee recommended the introduction of TCV for infants and children over 6 months of age as a single dose in typhoid endemic countries. Routine programmatic administration of TCV is likely to be most feasible at existing vaccine visits at 9 months of age or in the second year of life.

It recommended that introduction of TCV should first be prioritized for countries with the highest burden of disease or a high burden of antibiotic-resistant S. Typhi. Uganda is not one of them.

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