The race is on in the United States for a Zika vaccine, but experts warn that despite some promising breakthroughs, a drug will not hit the market for years.
Much of the global effort to find a vaccine or cure for the Zika virus has been centred on the US of late, especially since the disease became prevalent in the country. But experts say a funding gap for research continues to hamper efforts - especially with large pharmaceutical companies staying on the sidelines and the US Congress dragging its feet on setting aside money for the disease.
"We need to invest more in addressing the Zika problem because one thing... missing right now is a vaccine for Zika," US Surgeon-General Vivek Murthy told CBS News.
"Now we have started phase one clinical trials but without additional funding to support the Zika response, we're not going to have the funds to continue that vaccine development ever."
President Barack Obama submitted a request in February for nearly US$2 billion (S$2.7 billion) in emergency funds to fight the virus but Congress has thus far failed to grant it, in part because Democrats and Republicans cannot agree on funding cuts to pay for the new package.
The government was forced instead to repurpose funds meant for other projects. Even then, many say the money will last only a few more months. And without a reliable source of public funding, the biggest players in the private sector have also been slow to invest.
"I can honestly tell you that it's very difficult on our part to keep some of these players engaged without a firm commitment from the government to help support the development of (Zika) vaccines," Dr Rick Bright, director of the influenza and emerging infectious diseases division in the Biomedical Advanced Research and Development Authority, told the health and life sciences news site Stat recently.
The unpredictable nature of vaccine research means major firms are tentative about investing resources without partnership with government. It is often unclear which vaccine candidate will succeed or if it will succeed before the epidemic blows over. For instance, many firms that rushed to develop an Ebola vaccine in 2014 found that the disease was under control before the drug could make it to market.
Still, the work that has taken place has been quick. Already, two clinical trials for Zika vaccines have begun and some 30 different research projects have cropped up in the past year - the bulk of them in the US.
The two separate human trials are being conducted by the National Institute of Allergy and Infectious Diseases and a Pennsylvania firm called Inovio Pharmaceuticals.
Inovio announced on Monday its second vaccine trial was under way in Puerto Rico, a US territory that has already recorded some 9,000 infections. There have been 2,500 Zika infections in the US mainland.
Another promising experiment comes from researchers testing existing drugs on the Zika virus.
Researchers found that a medicine known as Nicolsamide, commonly used to kill tapeworm, could be effective in battling Zika. If ultimately found to work in clinical trials, it could cut short the development process as Nicolsamide is not a new medicine.
For now, however, experts say a vaccine is still some time away. Said Dr William Schaffner of Vanderbilt University: "Even if everything goes very well... it will be a year or even more before we have a vaccine."