At a Congressional hearing in Washington, DC on Wednesday, officials from the Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH) say they are working closely with the US Food and Drug Administration (FDA) in their response to the Zika virus.

During the hearing, CDC Director Tom Frieden and Anthony Fauci, director of the National Institutes of Allergy and Infectious Disease (NIAID) briefed members of the House Foreign Affairs Committee on their response efforts and a possible timeline for a vaccine against Zika.

Last week, the World Health Organization (WHO) declared the association between Zika and clusters of microcephaly in Brazil and French Polynesia to be public health emergency. On Monday, President Obama requested $1.8 billion in funding for the US effort to fight the disease.

During his testimony, Frieden told Congress that the CDC has uncovered new evidence supporting the link between Zika and microcephaly:

"Among four infants, two miscarriages at age 10 and 11 weeks … and two infants who tragically had microcephaly and died within the first 24 hours of life. Working with our Brazilian colleagues, the CDC laboratory was able to identify the genetic material of the Zika virus in the brain tissue of the two infants who died with microcephaly."

"This is the strongest evidence to date that Zika is the cause of microcephaly, but it's still not definitive," he said.

According to Frieden, aside from rubella and cytomegalovirus, the CDC is not "aware of any other viral cause of a significant number of birth defects [and is] not aware of any prior mosquito-borne cause of fetal malformations."

Vaccine Timeline

Because no drugs or vaccines exist to treat of prevent Zika, health authorities are focusing on preventive and vector control measures, such as wearing long sleeves when outdoors, avoiding travel to Zika-affected regions and using pesticides and other measures to control mosquito populations.

However, Fauci says the NIH's ultimate goal is to develop a vaccine against the disease, something he is optimistic about.

"We feel pretty confident that we'll … be able to do preclinical [studies] by the summer … which means we'll be finished by the end of 2016," Fauci said.

Then, if "the outbreak is still raging, you could go into an accelerated Phase IIa/IIb, which means you could likely determine if it's effective in six to eight months, and if it is, you can get an accelerated approval from the regulatory bodies," referring to FDA's accelerated approval pathway, which has been used to approve products based on Phase II studies in the past.

Given that pace, Fauci believes a vaccine could be ready by the end of 2017, "which is really rocket speed for a vaccine," he said.

Fauci is also confident that commercialization of a vaccine will not be an issue.

"We're already … having calls from … big pharmaceutical companies interested in partnering with us," he said.

FDA Involvement

Both Frieden and Fauci praised FDA for its involvement with their efforts.

"We've been working very closely with the FDA, and in both Ebola and Zika, they've been able to rapidly allow us to use effective test technologies within a day or two of our asking," Frieden said.

Speaking for NIH, Fauci said his staff have been "working very closely with [FDA] right from the get-go."

When developing treatments, he said, it's best to "involve the FDA right from the very beginning of a project. You don't do it and then go to the FDA and see how you can get something approved. They work with us right from the beginning … we're very optimistic about that relationship."

Joint Subcommittee Hearing: The Global Zika Epidemic