WHO: Zika vaccines at least 18 months away from broad trials

GENEVA — Possible Zika vaccines are at least 18 months away from large-scale trials, the World Health Organization said Friday as it advised pregnant women to consider delaying travel to areas where the mosquito-borne virus has turned up amid concerns it may be linked to abnormally small heads in newborns.

Marie-Paule Kieny, WHO's assistant director-general for health systems and innovation, says the U.N. health agency's response is "proceeding very quickly" and that 15 companies or groups have been identified as possible participants in the hunt for vaccines.

"(But) our knowledge of what is currently in the pipeline tells us that it will take approximately 18 months before a vaccine can be launched into large-scale trial to demonstrate efficacy," Kieny told reporters in Geneva.

Concerns have grown in recent months about a Zika outbreak that has affected at least 33 countries — mostly in South and Central America. In Brazil, the epicenter of the outbreak, the spike in cases has coincided with a mysterious rise in cases of microcephaly, or abnormally small heads, in newborns.

WHO believes the link between the virus and microcephaly in some newborns is "more and more probable," Kieny said, but added it will likely take "weeks to a few months" to determine whether a firm link exists.

To try to confirm a link, researchers in Colombia are tracking what happens to pregnant women who have been infected with Zika, Marcos Espinal of the Pan American Health Organization told reporters at the American Association for the Advancement of Science meeting in Washington. Separate studies also are being conducted in Brazil.

"What everybody would like us as public health officials to say is, now we've proved it. It's not going to be like that," Christopher Dye, WHO's director of strategy, added at the briefing in Washington.

But to protect the public, "we have to consider that Zika is guilty unless proven innocent," Dye said.

Kieny said that different types of possible vaccines — such as live or killed virus, or the use of DNA vaccines — may lead to differences in timing on development, but developers "are all starting at a very basic level."

WHO also issued updated guidelines about travel to Zika-affected areas, saying pregnant women should talk to their health care providers and "consider delaying travel to any area where locally acquired Zika infection is occurring."

Previously, the world health body had only advised women who are pregnant, or hoping to become pregnant, to protect themselves from the bites of the mosquito that transmits the Zika virus.

The agency noted that the virus was not spread by person-to-person contact "though a small number of cases of sexual transmission have been documented." WHO advised men and women returning from Zika-affected areas to practice safe sex "including through the correct and consistent use of condoms," but didn't specify for how long.