Ana Beatriz, a baby girl with microcephaly, celebrates her 4-month-birthday  in Lagoa do Carro, Pernambuco, Brazil, on Feb. 8. Increasing cases of microcephaly have been observed lately in regions where the Zika virus has been spreading. (Percio Campos/EPA)

National Institutes of Health officials said this week that researchers may be closer to developing a Zika vaccine than previously thought and that tests on human subjects could begin in as soon as a few months.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said in an interview that government scientists have been able to leverage previous research done on two similar viruses — West Nile and dengue — to very quickly create vaccine candidates that target Zika. The researchers are now working on fine-tuning the vaccines and in manufacturing enough of to be able to test it on 20-30 healthy individuals this summer. Fauci said he is optimistic an experimental vaccine would pass those initial tests and would be ready for a larger-scale trial in early 2017.

"You never say guaranteed in medicine," Fauci said, "but I would be really surprised" if it isn't ready.

Based at the National Institutes of Health's main campus in Bethesda, the national Vaccine Research Center was created in 2000 by former president Bill Clinton to focus on an HIV/AIDS vaccine. It now employs about 250 people and has an annual budget of $100 million and a broader mandate that includes work on a universal flu vaccine to ones that target malaria and other leading killers.

John Mascola, who directs the Vaccine Research Center, said that unlike some pathogens for which developing a vaccine is very challenging, making one for Zika "should be quite feasible" based on what we know about its structure and DNA.

He said that NIH is actively speaking with commercial partners to try to prepare for the possibility that the vaccine they are working on would be effective and would still be needed next year. In that situation, NIH would hand off the vaccine to a company that could produce and distribute it rapidly on what could be a global scale.

A number of private efforts are also underway. Sanofi Pasteur, the vaccine division of the French pharmaceutical giant, for instance, said Feb. 2 that it had launched a Zika project, as has South Korea's GeneOne Life Science.

The World Health Organization said in a briefing Friday that the vaccine landscape is "evolving very rapidly and numbers change daily" but that it had identified about 15 companies or groups that are working on a vaccine. Most of the work is at a very early stage, but there are two projects that are more advanced — the NIH DNA vaccine and an inactivated vaccine from Bharat Biotech in India.

The WHO had a more conservative timeline than the NIH for when the vaccines might be ready for large-scale tests, saying that this may be at least 18 months away.

Developing vaccines is typically a long and arduous process, taking at least a couple of decades and an estimated $1.5 billion in investments. That's why in recent years, many big pharmaceutical companies have scaled back vaccine research efforts and focused their efforts on developing newer versions of already existing vaccines.

This post has been updated.

Correction: A previous version of the story incorrectly referred to the development of a hybrid vaccine. The National Institutes of Health is working on several Zika vaccine candidates using different approaches.

Read more:

Why Zika is a ticking 'time bomb' for Latin America

Zika and sex: What you need to know about the case in Dallas

FAQ: What is Zika, and what are the risks as it spreads?

‘Zika isn’t important': The infuriating case of a scientist’s search for funding.

What this amazing mom of two girls with microcephaly has to say about Zika scare

For more health news, you can sign up for our weekly newsletter here.