Officials with the Strategic Advisory Group of Experts on Immunization and WHO discussed recommendations for new vaccines — including one that researchers said could significantly reduce typhoid fever cases — during a press conference Oct. 24.
The recommendations come from a semiannual meeting of the advisory group (SAGE) — a committee that advises WHO on global immunization policy — held the previous week in Geneva, Switzerland.
At the meeting, SAGE discussed the prevalence of typhoid fever and increased antimicrobial resistance of Salmonella Typhi in low- and middle-income countries.
In response, SAGE is recommending the introduction of a typhoid conjugate vaccine for children in countries where typhoid fever is endemic.
Researchers evaluated the Vi-tetanus toxoid vaccine (Vi-TT) in a phase 2b study published in September in The Lancet. In the study, 112 people were vaccinated and then challenged orally with an S. Typhi wild-type strain isolated from a chronic carrier in the United States. The researchers estimated that Vi-TT is 87.1% effective, based on an expanded definition of typhoid fever.
Given the potential efficacy of the vaccine, SAGE said countries with the greatest burden of disease and antimicrobial-resistant S. Typhi should be a priority for the vaccine’s introduction, adding that catch-up immunization should be prioritized to the youngest patients — those aged 15 years old and younger — depending on the epidemiology of their area.
SAGE chair Alejandro Cravioto, MD, PhD, of the faculty of medicine at the Universidad Nacional Autónoma de México, emphasized the role of vaccines in combatting antimicrobial resistance.
“The idea of using vaccines to reduce antimicrobial resistance is something essential and has been highlighted as one of the main objectives of the new director-general of the WHO,” Cravioto said, referring to Tedros Adhanom Ghebreyesus, who was elected director-general in May.
Cravioto also highlighted progress in rabies prevention, including pre-exposure prophylaxis (PrEP), post-exposure prophylaxis (PEP) and rabies immunoglobulin (RIG).
“We have a review of new rabies vaccines, new vaccines against this horrible disease, that allow us to shorten the time after someone is exposed to the virus … to a regimen that [is administered] in 1 week instead of a whole month, which is really an improvement in the way we can handle the protection of individuals at risk of developing this severe disease,” Cravioto continued. “We looked into how to more efficiently use the immunoglobulin we have against rabies, which is very expensive and should be used sparingly, mainly at the site where the bite has happened.”
SAGE recommended two PrEP regimens for all age groups of healthy people. One is administered intradermally at two sites on days 0 and 7, whereas the other is given intramuscularly at one site on days 0 and 7.
SAGE also concluded that three PEP regimens are also effective. One is administered intradermally at two sites on days 0, 3 and 7; another is administered intramuscularly at one site on days 0, 3, 7, and between 14 and 28 days; and the third given intramuscularly at two sites on day 0, then at one site on days 7 and 21.
Cravioto said SAGE recommendations on administering RIG can make rabies prevention more efficient. The group determined that trials indicate that RIG in and around a bite wound neutralizes the rabies virus within only hours.
“So, the idea here is to totally put the antitoxin (RIG) on the site where the dog has bitten the person,” Cravioto said. “Then the rest of the dose can be used for other purposes, but it doesn’t need to be given at a different site to the same person. I think this eliminates cost. And the antitoxin, which is not easily available in many places, can be used for several patients.” – by Joe Green
Jin C, et al. The Lancet. 2017;doi:10.1016/S0140-6736(17)32149-9.
WHO. Summary of the October 2017 meeting of the Strategic Advisory Group of Experts on Immunization. www.who.int/immunization/policy/sage/SAGE_oct_2017_meeting_summary.pdf?ua=1. 2017. Accessed October 24, 2017.
Disclosures: Cravioto reports no relevant financial disclosures. Please see the following link for other SAGE members’ relevant financial disclosures: