5 QUESTIONS

The world has been waiting for years for an effective Ebola vaccine. But there are still unanswered questions. Here are a few:

1 How long will the vaccine’s protection last?

The trial shows this vaccine — currently called rVSVZEBOV — likely will be very useful as a tool to snuff out outbreaks.

Only one dose of vaccine is needed and protection kicks in fast, within about six days. Those are great characteristics when you’re trying to stop spread of a deadly virus.

But no one yet knows how long that protection will last. People who were vaccinated will have to be followed for years to see whether their immunity starts to wear off.

2 What does this mean to the other Ebola vaccines in development?

Most vaccines target diseases that are common. They cost hundreds of millions of dollars to develop, but the expense is recouped through ongoing sales.

That won’t be the case with an Ebola vaccine. Despite the massive West African outbreak, Ebola is a rare disease. No country would consider vaccinating all its children against Ebola, for example. It wouldn’t make economic sense.

3 Is there room for any other Ebola vaccines?

Sure. Some of the other candidates might provide longer lasting protection, though they’ll need to be given in several doses over a period of months.

That kind of delivery strategy doesn’t work well for outbreak control. But it could protect health-care workers.

4 Can this vaccine be used to stop all future Ebola outbreaks?

Probably not. There are five known strains of Ebola. This vaccine protects against Ebola Zaire. Studies suggest a vaccine that protects against Ebola Zaire won’t protect against the Sudan or Bundibugyo strains. So, vaccines that protect against them will need to be made, as well.

5 Will this vaccine help end the West African outbreak?

That’s a definite possibility. The trial in Guinea will now offer vaccine to contacts of any new Ebola cases, which should help stop transmission there. Talks will soon begin with the government of Sierra Leone.