Zika Vaccine Still Years Away- Says W.H.O.

More than 60 research institutes and companies are working on products to combat the spread of the Zika virus, the World Health Organization said Wednesday, but a vaccine is likely to take years to develop and may come too late for the outbreak now sweeping across Latin America and the Caribbean.

Vaccine development was one of three priorities global health experts identified at a meeting in Geneva where they are taking stock of gaps in what is known about the disease and setting plans to accelerate the development of countermeasures.

Eighteen organizations are working on developing a vaccine for the Zika virus, but the most advanced product is still months from starting human clinical trials, and the release of a vaccine is still “years away,” Marie-Paule Kieny, an assistant director general at the World Health Organization, said at a news conference at the end of the meeting.

It was therefore possible, she said, that a vaccine would come too late for use in the current outbreak of Zika, which has swept across 31 Latin American and Caribbean countries and territories.

Expecting a vaccine in three years was “optimistic,” Jorge Kalil, director of Brazil’s Butantan Institute, one of the organizations developing a vaccine, said at the news conference. “Of course we will try to do it in less, but I think it will be almost impossible.”

Some researchers, including those at the National Institutes of Health, hope to start human trials this fall, but testing is unpredictable and, as with Ebola, the epidemic could be over before a vaccine is ready.

Since Zika is harmless to most people infected by it, Dr. Kieny said, “the most pressing need” at this stage of the response is developing diagnostic and preventive tools, in particular tests that could distinguish Zika from related diseases like dengue and chikungunya.

Health experts are also grappling with measures that could be taken to limit exposure to the mosquitoes that spread the disease. Spraying insecticides to kill mosquitoes has had no evident effect on halting the spread of dengue fever, raising concerns that it may be equally ineffectual in checking the spread of the Zika virus, Dr. Kieny said.

In the absence of any other proven control measures, spraying should continue for the moment, she said. But, she added, health authorities need to focus more on mobilizing families and communities to protect themselves by eliminating mosquitoes from their homes.

The World Health Organization will hold an emergency meeting of a “vector control advisory group” to consider possible interventions. “We must be sure that we invest in interventions that work,” Dr. Kieny said.

Health experts are considering releasing irradiated and genetically modified mosquitoes that limit reproduction to reduce the size of mosquito populations, but Dr. Kieny cautioned that those potential remedies needed to be evaluated with “extreme rigor.”

Other experts have noted that those methods have been tested only in field trials in which about 100,000 mosquitoes are released at a time to protect one neighborhood; the Zika virus, however, is now in many millions of mosquitoes across two continents, so it will be years before such methods are ready.

Meanwhile, researchers are still trying to determine the types of mosquito that can spread Zika. In the tropical climate of Latin America the main vehicle of transmission has been the Aedes aegypti mosquito, but Dr. Kieny said researchers had found that other species more adapted to temperate climates might also spread the virus.

“It may well be that the space where Zika is transmitted may be larger, broader” than the tropical areas where the Aedes species flourishes, she said.

Source: New York Times.