Why existing vaccines won’t help this Ebola outbreak

Key Points:

• The first Ebola vaccine was developed in the 1990s primarily to counteract Soviet bioweapon threats, not in response to an outbreak, with a breakthrough coming from a weakened vesicular stomatitis virus (VSV) displaying Ebola glycoproteins.
• The existing VSV-based Ervebo vaccine, effective against the Zaire Ebola virus, does not reliably prevent transmission of the rarer Bundibugyo Ebola species due to significant differences in their surface glycoproteins.
• New vaccine candidates targeting Bundibugyo are being fast-tracked, including VSV-based prototypes, an adenovirus-based ChAdOx1 vaccine, and an mRNA vaccine from Moderna, each with distinct advantages and challenges regarding efficacy, side effects, and production speed.
• None of the current candidates provide broad protection against all Ebola species; researchers aim to develop a universal vaccine targeting shared viral components, a goal that requires more time and ongoing research beyond outbreak periods.
• The Coalition for Epidemic Preparedness Innovations (CEPI) is investing nearly $62 million in developing these new vaccines and has launched a five-year strategy to accelerate the creation of broadly protective Ebola vaccines for future outbreaks.