Zika Vaccine May Come Too Late

U.S. scientists could know by early 2018 whether they have a working vaccine for Zika virus, according to Anthony Fauci, the head of the U.S. National Institute of Allergy and Infectious Disease. But that’s the best case scenario, and uncertainty over how rapidly the mosquito-borne disease will spread in the coming months and years makes it difficult to predict how quickly a vaccine could be developed.

Collecting necessary data about a potential vaccine’s effectiveness will depend in part on the incidence of the disease in the communities that participate in the tests. But if enough people who have already been exposed to the disease naturally develop immunity, it could cause the virus to spread less quickly and hamper data collection.

Zika has been spreading rapidly in Latin America for several months. Thus far, there have been 426 reported cases of Zika on the U.S. mainland, all associated with travel from affected regions, according to the Centers for Disease Control. There have also been 599 cases in U.S. territories Puerto Rico, American Samoa, and the U.S. Virgin Islands. Of those cases, 596 were acquired locally, and 570 of those were in Puerto Rico. Fauci said yesterday it is “very likely” that the mainland will see local outbreaks as the weather gets warmer.

Most people who get the disease will experience only mild symptoms or may not even be aware that they have it, but the virus is known to cause birth defects if it infects pregnant women.

Fauci said the $1.9 billion the White House has asked Congress to devote to addressing the Zika outbreak is “absolutely essential.” A debate over the funding has stalled in the Senate. 

The urgency of the outbreak has led some scientists to suggest more radical approaches than a vaccine, like deploying gene drives. That technology, the risks of which are not well understood, could theoretically eliminate whole populations of mosquitoes by using the gene editing tool CRISPR to induce a genetic change that spreads as the insects reproduce. And it might only take months to a year to develop.

(Read more: Science, NBC News, “We Have the Technology to Destroy All Zika Mosquitos”)