Clinical trial with unlicensed yellow fever vaccine in Japan

Enhanced safety surveillance of STAMARIL® yellow fever vaccine provided under the expanded access investigational new drug program in the USA

BACKGROUND

YF-VAX® (Sanofi, Swiftwater, PA), a live, attenuated vaccine based on the yellow fever (YF) substrain 17D-204, is the only YF vaccine licensed in the USA. Manufacturing disruption of YF-VAX and anticipated depletion of the US supply by mid-2017 led to the importation of another YF vaccine, STAMARIL® (Sanofi, France), into the USA under an expanded access investigational new drug program (EAP) to fulfil the public health need for YF vaccination. As part of this program, Sanofi collected enhanced safety surveillance data following vaccination with STAMARIL. Here, we report the results of the enhanced safety surveillance.

METHODS

STAMARIL vaccine was offered to those aged ≥9 months at high risk of YF. Vaccine recipients (or parents/guardians) were instructed to report suspected adverse reactions, any serious adverse events (SAEs) including adverse events of special interest [AESI] occurring after vaccination regardless of suspected relationship, and any inadvertent exposure in pregnancy or breastfeeding within 14 days of vaccination. The AESIs monitored were anaphylaxis, neurotropic disease (YEL-AND) and viscerotropic disease (YEL-AVD).

RESULTS

Overall, 627 079 individuals received STAMARIL from May 2017 through June 2021; of these, 1308 (0.2%) reported at least one AE, of which 122 reported at least one SAE. There were seven cases of YEL-AND and three cases of YEL-AVD reported, for reporting rates of 1.1 and 0.5 per 100 000 vaccine recipients, respectively. One vaccine recipient developed an anaphylactic reaction (reporting rate: 0.16 per 100 000). No safety concerns were identified from inadvertent vaccine exposure during pregnancy (41 pregnant women) or potential neonatal exposure via breast milk (four exposed infants).

CONCLUSIONS

This study supports the utility of STAMARIL in the EAP as an alternative solution for the YF vaccine shortage in the USA. SAEs were very rare and consistent with the known safety profile of STAMARIL.

A nationwide prospective cohort study on safety of the 17D-204 yellow fever vaccine during a vaccine shortage in Japan

In response to the vaccine shortage of yellow fever vaccine (YF-VAX) due to manufacturing delays, the unapproved 17D-204 YF-VAX was used as an investigator-initiated clinical trial in Japan. The vaccine was administered to 11,279 participants in 19 YF vaccination centers in Japan, and few serious adverse events were observed.

Yellow fever control: current epidemiology and vaccination strategies

Yellow fever (YF) outbreaks continue, have expanded into new areas and threaten large populations in South America and Africa. Predicting where epidemics might occur must take into account local mosquito populations and specific YF virus strain, as well as ecoclimatic conditions, sociopolitical and demographic factors including population size, density, and mobility, and vaccine coverage. Populations of Aedes aegypti and Aedes albopictus from different regions vary in susceptibility to and capacity to transmit YF virus. YF virus cannot be eliminated today because the virus circulates in animal reservoirs, but human disease could be eliminated with wide use of the vaccine. WHO EYE (Eliminate Yellow Fever Epidemics) is a welcome plan to control YF, with strategies to be carried out from 2017 to 2026: to expand use of YF vaccine, to prevent international spread, and to contain outbreaks rapidly. YF vaccination is the mainstay in controlling YF outbreaks, but global supply is insufficient. Therefore, dose-sparing strategies have been proposed including fractional dosing and intradermal administration. Fractional dosing has been effectively used in outbreak control but currently does not satisfy International Health Regulations; special documentation is needed for international travel. Vector control is another facet in preventing YF outbreaks, and novel methods are being considered and proposed.