Single-Dose Typhoid Vaccine 84% Effective in Africa Trial

By Gene Emery

September 16, 2021

NEW YORK (Reuters Health) - A single dose of the Vi-TCV typhoid fever vaccine was more than 80% effective in a test of 28,130 Malawian children aged nine months to 12 years, according to new research.

There were 46.9 confirmed cases of typhoid per 100,000 children per year in the group that received Bharat Biotech's Typbar-TCV vaccine versus 243.2 cases among children who received Serum Institute of India's meningococcal capsular group A conjugate (Men A) vaccine as a control, a significant difference. Follow-up lasted for up to 24 months.

The findings appear in the New England Journal of Medicine.

Although the World Health Organization (WHO) has recommended the vaccine since 2017 for children six months and older who live where typhoid is endemic, this is the first test of the vaccine in Africa. Two other tests are underway in Asia.

Older typhoid vaccines have been less effective, particularly in pre-school children, coauthor Dr. Melita Gordon, a professor of global health at the University of Liverpool, in the U.K., told Reuters Health by phone. But the disease "really is affecting the younger children as much as the older children, and this vaccine works equally well in younger and older children," according to the new results.

The number of serious adverse events after six months was 50% higher in the MenA group than among the typhoid recipients and none of the six deaths occurred among the children who received the typhoid vaccine.

"No serious adverse events were considered by the investigators to be related to vaccination," the researchers write.

"This is the evidence many African governments will want to see, both in overall efficacy and efficacy in younger children as well," Dr. Gordon said.

"Malawi and the rest of Africa needed this vaccine yesterday, and we are thrilled to have a safe effective vaccine now," Dr. Queen Dube, chief of health services at the Malawi Ministry of Health, said in a news release.

Based on the findings, the country is planning mass vaccination in September 2022 and the shot will be subsequently included in routine vaccination schedules.

Typhoid fever kills more than 110,000 people worldwide each year and infects more than 9 million. In some urban settings, the disease strikes up to 843 people per 100,000 people per year. In Malawian children, the case fatality rate is 2.1%, and 3.6% of youngsters who become infected develop small-bowel perforation.

An effective vaccine is particularly needed because the disease has become resistant to fluoroquinolones and other antibiotics.

"The timing is very fortuitous," Dr. Gordon said. "This vaccine was developed as we saw multidrug-resistant typhoid jump from Asia to Africa and sweep across Africa from 2010 onward."

The new field trial also suggests that the benefits of the vaccine persist. Its effectiveness was 84.6% at 12 months, 82.9% at 18 months and 78.7% at 24 months.

"The old vaccines were on the order of about 50% effective over a 3-year period," said Dr. Gordon. "We have every reason to think, based on our current data and what we see with other conjugate vaccines against other pathogens, that the immunity and protection will be far longer lasting."

A shot costs about $1.50.

"It's not just cost-effective per dose. Nearly 50% of typhoid episodes that happen in Africa hit families as a catastrophic expense that can tip a poor family into poverty. Parents lose their job, kids don't get their schooling," said Dr. Gordon.

Zimbabwe and Liberia are also planning mass immunizations with the vaccine, she said.

SOURCE: https://bit.ly/3k5FWMW The New England Journal of Medicine, online September 15, 2021.

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