The start of a vaccination program this week in the Democratic Republic of the Congo, a first in an Ebola outbreak, was a cause for a mini celebration in research and outbreak response circles. But there are challenges ahead in the real-world use of the vaccine, warned the head of the global health organization that is funding the vaccination effort.

Successful use of the vaccine requires response planners and vaccination teams to hit the right notes on several challenging communications messages, said Dr. Seth Berkley, CEO of Gavi, the Vaccine Alliance, a public-private partnership that assists developing countries with immunization programs.

Getting those messages wrong could endanger lives and undermine the effort to use vaccine to help extinguish this outbreak, said Berkley, who made a whirlwind trip over the weekend from Geneva to western DRC, where the outbreak is happening, to witness the start of the vaccination

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Likewise, the design of the program, which is called ring vaccination, can only succeed if disease detectives on the ground can provide vaccination teams with a thorough list of the people who should be vaccinated — people who are at risk of developing the disease because they are health care workers, or because they were in contact with someone who contracted Ebola.

“There is a danger that vaccines get seen as the holy grail,” Berkley told STAT. “That is a problem because the main thing that’s going to control this epidemic is the traditional way of dealing with Ebola. And that’s getting the epidemiology under control, understanding what the contacts are, getting isolation, safe burial — all those things.”

“I’m a great fan of vaccines. We need to get them out,” continued Berkley. “But they rely on those other things, and we need to make sure that both are going in parallel.”

The vaccination effort started Monday with immunizing health care workers in Mbandaka, the capital of Equateur, the province where the outbreak is taking place. There are more than 7,500 doses of the vaccine, made by Merck, on the ground already, and the company has been asked by the World Health Organization to send another 8,600, a Merck spokesperson said.

In an interview posted on Twitter on Tuesday, Dr. Peter Salama, the World Health Organization’s deputy director-general for emergency preparedness and response, said the hope is that roughly 1,000 people will be vaccinated over the next week.

“We’re really on an epidemiological knife-edge here,” Salama told Devex, a media platform for the international development community. He said the discovery of a number of cases in Wangata, a district within Mbandaka, changed the WHO’s estimate of the threat posed by this outbreak. More than 1 million people live in Mbandaka, which is located along the Congo River — a major transportation route that links the outbreak zone to large cities to the north and south.

To date in this outbreak, there have been 58 cases and 27 deaths. The DRC declared the outbreak on May 8, but the WHO says cases date back to early April at least. The outbreak’s potential for spread within DRC and to surrounding countries has the WHO and other response agencies on high alert, but a panel of expert advisers said last Friday that the situation does not currently constitute a global health emergency.

The vaccine was tested at the tail end of the 2013-2016 West African outbreak, in a ring vaccination trial. The ensuing study declared that the vaccine was 100 percent effective; there were no infections among people who received the vaccine at least 10 days earlier.

Contacts who developed Ebola in the nine days after vaccination were excluded because they would have been infected before they were vaccinated, or contracted the virus before their immune systems had time to mount a response to the vaccine.

Those findings give people hope this vaccine will help control Ebola outbreaks. But the 100 percent effective figure from the Guinea trial will create high expectations that paradoxically could work against the vaccine in the real world.

Vaccinators will need to carefully explain that some people who receive the vaccine may still get sick because protection is not immediate or because some of them may already have been infected when they were vaccinated, Berkley said. Otherwise, people may assume the vaccine doesn’t work, or, worse, may wrongly conclude the vaccine can cause Ebola. Those kinds of rumors could profoundly affect people’s willingness to be vaccinated.

Likewise, health workers — a key population being targeted by this campaign — need to understand that they can’t let their guard down when it comes to treating Ebola patients, he said. “You want health workers to continue to use maximum precautions regardless of whether they’re vaccinated or not.”

In the real world, no vaccine is 100 percent effective. And while this vaccine appears to generate a rapid immune response, it is not immediate.

“One of the challenges is making sure that those messages are really heard and understood in both the health community … and then certainly in the more general community,” Berkley said.

Another risk: No one knows how long protection with this vaccine lasts. A recent study reported the protection may last as long as two years in some people, but the reality is only about 16,000 people in total have ever been vaccinated with this product, and most of those vaccinations occurred within the last two to three years.

Another communication challenge Berkley foresees stems from the fact that the vaccination effort is not a mass vaccination campaign. There is no attempt — and no need — at this point to try to vaccinate everyone.

He’s concerned the “worried well” will show up demanding a shot. Said Berkley: “So the idea that there is only a subset of people who are going to get it is complicated. And people don’t understand that. And so education is going to be very important.”

Still another challenge will be the fact that the vaccine is what is called “reactogenic.” As it activates the immune system, people can feel ill and even develop a fever. In the middle of an outbreak, people who have been in contact with Ebola cases and who develop a fever could be mistaken for Ebola patients themselves.

During the vaccine trial in Guinea, people who received vaccine were given acetaminophen or other over-the-counter drugs used to lower fever. And that is part of the plan in DRC, Berkley said. “And obviously if somebody doesn’t get better or the fever gets worse, then they will be triaged in a different way.”

This story has been updated with new cases totals from the WHO.

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