Even if the world’s largest drugmakers were to mobilize as fast as they could, and even if the science were straightforward, it’s unlikely a Zika vaccine could be developed quickly enough to address the expanding outbreak of the mosquito-borne virus that may cause birth defects when pregnant women are infected.

Little work has been done so far on the virus, which the World Health Organization said last week is “spreading explosively” in Latin America after a spike in cases of microcephaly, a birth defect that causes babies to be born with abnormally small heads. In addition, previous vaccine development has shown that it takes years, sometimes decades, to come up with a product that’s safe and effective.

“Vaccines as well as antivirals take time to develop, and I would not expect that anything will be available for use in the course of the current issue that’s going around the world,” said Robert Amler, dean and professor of public health at New York Medical College.

Dengue fever has inspired 14,840 academic papers and hepatitis C is the subject of 73,764, yet there have been only 242 papers published about Zika, according to data from the National Center for Biotechnology Information in Bethesda, Maryland. There’s simply a “data vacuum” when it comes to the virus, said Cameron Simmons, professor of microbiology and immunology at the University of Melbourne’s Nossal Institute for Global Health.

Dengue Vaccine

Then there’s the time it takes to develop vaccines. Sanofi Pasteur, the vaccine division of the French drugmaker, spent 20 years working on the world’s first dengue vaccine, which was approved in December. Even with that under its belt, Sanofi, which is looking into the possibility of developing a Zika vaccine, didn’t sound overly optimistic about it happening anytime soon.

“There are too many unknowns about Zika to reliably judge the ability to research and develop a vaccine effectively at this time,” Sanofi spokeswoman Mary Kathryn Steel said. “Our successful experience with dengue vaccine development has shown us that it is important to have robust documentation of the disease and scientific understanding of how viruses work when initiating vaccine development.”

GlaxoSmithKline Plc, which has a vaccine division, said it doesn’t have a Zika vaccine candidate in development, although it has “reached out to our partners and collaborators in Brazil and across the world to assess the situation and feasibility of potential vaccine development,” spokeswoman Gwynne Oosterbaan said. Vaccine research and development is a “lengthy process,” she said, normally taking 10 to 15 years.

Extra Precautions

Another complicating factor is that the people who appear to be at the highest level of risk from Zika are pregnant women, a population that requires extra precautions when it comes to administering drugs.

“Even if you can develop it overnight, the approval process is very long, and of course we have seen all of these issues with Zika in pregnancy that we have not seen before,” said Stephen Higgs, president of the American Society of Tropical Medicine and Hygiene and the director of the Biosecurity Research Institute at Kansas State University. “So these vaccines have to be proven to be safe and effective in pregnancy.”

Understanding the Virus

Then there’s the question of how to use a vaccine. Determining which population to treat will depend in part on understanding the disease better, said Mike Catton, director of the Victorian Infectious Diseases Reference Laboratory in Melbourne.

“I don’t think they’re probably at the point yet where they have a handle on the prospective risk of microcephaly in pregnancy, what trimester, is it everybody, what proportion of women, what co-factors,” he said. “You need a good grasp of all of that before you made a public health decision to put a scarce dollar into a Zika vaccine.”

Still, companies are taking a look inside their own research labs to see what can be done, and how quickly.

“We are absolutely looking at that as what should we do and what can we do,” said Paul Stoffels, chief scientific officer at Johnson & Johnson. “We might have mechanisms to treat or prevent with vaccines, but we are nowhere in having products for that.”

Animal Testing

There are smaller companies working on a vaccine as well. A spokesman for Inovio Pharmaceuticals Inc. said the company believes it’s in the lead in developing a Zika vaccine, having begun research late last year. Inovio plans to complete animal testing in the third quarter and is “fully prepared” to start a human study of its vaccine before the end of this year.

Experts say that controlling the spread of mosquitoes may be an easier way to slow -- or halt -- the spread of the virus.

“Without a vaccine, you really need to focus on the vector,” said Roy Hall, professor of virology at the University of Queensland in Brisbane, Australia, referring to the type of mosquito that spreads the virus. “But you also need really good surveillance -- to be able to know where the mosquito is.”

Genetically modified mosquitoes might be used to help fight the Zika virus and are getting urgent attention from U.S. regulators. The Food and Drug Administration is reviewing an application from Intrexon Corp. to conduct a field trial of the mutant bugs in Florida. (Bloomberg)