Adding Zika Virus to the FDA Priority Review Voucher Program Act (Public Law 114–146)

The Policy

What it does

Adds the Zika virus to the list of tropical diseases under the FDA’s priority review voucher program, an incentive program to encourage pharmaceutical companies to develop faster treatments for threatening tropical diseases.


This bill reflects the gravity of the threat of the Zika virus to the health United States citizens and the urgency with which Congress is responding to the threat.

  • Public Law 114–146 mandates the Food and Drug Administration (FDA) add Zika virus to the list of tropical diseases under its priority review voucher program.

The Priority Review Voucher program

  • This voucher program incentivizes pharmaceutical companies to develop drugs to treat or prevent diseases on the list of qualified tropical diseases to minimize their threat to national public health.
  • Vouchers operate by providing pharmaceutical or drug companies (the “sponsor”) that bring the FDA a human drug application aimed at particular diseases an opportunity to obtain priority review for subsequent drug applications of that sponsor.
    • Note that sponsors may transfer vouchers as they see fit.
  • Priority review entitles the holder to have a future new drug or biological product application acted upon by the FDA within six months.

The 1992 Prescription Drug User Fee Act (PDUFA) set a 6-month goal for priority review of new drug applications (NDAs) versus a 10-month goal under standard review. In FY2009 and FY2010, 78% of priority NDAs and 94% of standard NDAs were reviewed on time, according to the 2010 PDUFA Performance Report (p. 10).


The Science

Science Synopsis

  • The Zika virus is contracted primarily through an infected Aedes mosquito bite, but can also be spread through mother to child transmission, sexual transmission, and blood transfusion.
  • The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. Infection does not necessarily confer demonstration of symptoms.
  • The incubation period, or time between exposure and symptoms, is unknown, but is thought to be between a few days and a week.
  • Zika virus poses an especially dangerous threat to pregnant women, as it is associated with microcephaly, a condition in which a baby’s head and brain are abnormally small and the brain does not properly develop. This can lead to cognitive impairment, vision and hearing problems, seizures, and other brain-related impairments.
  • Zika virus is also associated with Guillain-Barré Syndrome (GBS), a nervous system condition that can lead to muscle weakness or temporary paralysis.
  • The CDC developed the first commercial test to detect whether a person has been infected by the Zika Virus (Zika MAC-ELISA). This test must be conducted between 2 and 12 weeks post infection.  The MAC-ELISA test has the potential to identify a false positive if antibodies from a similar virus (dengue or chikungunya) are present.  The test can indicate a false negative if the sample is collected more that 12 weeks after the infection, or if antibody concentration is too low. Relevant samples include serum and cerebrospinal fluid.
  • The CDC also developed the Trioplex rRT-PCR laboratory test, which is designed to detect Zika virus and two other viruses (dengue and chikungunya) also spread by mosquito bites. This test must be conducted within 7 days of onset of symptoms.  The test is designed to have a low false positive rate. However, false negatives are also possible for this test; a negative result does not rule out infection by Zika. Samples from this test can be gathered from urine, cerebrospinal fluid, serum or amniotic fluid.
  • There is currently no cure or vaccine for Zika virus. 

The Debate

Endorsements & Opposition

There is general support for adding Zika virus to the eligible list of diseases under the priority review voucher program. The bill moved quickly through the Senate and will likely pass the House.

Support for the voucher program itself, however, is mixed. Some believe that the program isn’t necessary for companies to develop such drugs. Medicines san Frontiers argues that companies should be required to show they conducted the research necessary to obtain approval for the drug. Furthermore, vouchers do not require that companies that develop the drug actually need to sell it. The program also does not require the drugs developed for such tropical diseases to be affordable. It also does not preclude companies from developing a drug with the voucher that is marketed outside the U.S. Additionally, it may discourage innovation because the program incentivizes drug development, not other treatments. Some worry that the accelerated timeline of approval with the voucher by the FDA will cause the FDA to approve drugs without adequate consideration.