Zika vaccine begins 2nd phase of testing in U.S.

Researchers have begun thesecond phase of testing of a Zika vaccine developed by U.S.government scientists in a trial that could yield preliminaryresults as early as the end of 2017.

Dr. Anthony Fauci, director of the National Institutes ofAllergy and Infectious Diseases (NIAID), said on Friday the $100million UStrial has already been funded and will proceed,irrespective of the $7 billion in cuts to the NationalInstitutes of Health (NIH) budget proposed by the TrumpAdministration over the next 18 months.

In a conference call with reporters, Fauci would not commenton the proposed cuts because it is not clear yet what the actualbudget will be. Both Democratic and Republican lawmakers opposecuts to the NIH, which funds 21 institutes, including NIAID.

NIH Director Dr. Francis Collins is scheduled to speak with U.S. President Donald Trump later on Friday. "I will certainly betalking to Francis Collins when he returns from the WhiteHouse," Fauci said.

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Zika typically causes mild symptoms, but when the virusinfects a pregnant women, she can pass it to her fetus, causinga variety of birth defects including microcephaly, in which thebaby's head is abnormally small.

Fauci said the current Zika vaccine candidate had clearedpreliminary safety hurdles, and would now enter testing forefficacy, which would occur in two phases.

The first phase will continue testing for safety andevaluate the vaccine's ability to stimulate the immune system todevelop antibodies to fight Zika. It will also test different doses to see which works best.

The second phase, set to begin in June, will attempt todetermine if the vaccine can actually prevent Zika infection.

Several companies are developing Zika vaccines, includingSanofi SA, GlaxoSmithKline and TakedaPharmaceuticals.

In the NIAID study, researchers aim to enroll at least 2,490 healthy volunteers in areas with confirmed or potential activetransmission of Zika by mosquitoes. These include parts of the continental United States, Puerto Rico, Brazil, Peru, CostaRica, Panama and Mexico. They will receive either the vaccine,or a placebo, and be followed for two years.

If enough people are exposed to the virus, Fauci said theycould get an effectiveness signal as early as the end of this year. The trial is expected to be completed by 2019.

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Fauci said the government is already in discussions withpharmaceutical companies that would share the costs of the finalstage of testing and handle manufacturing.

Zika is primarily transmitted by mosquitoes, but it can alsobe transmitted sexually. According to Centers for DiseaseControl and Prevention, 5,182 people in the continental UnitedStates have been infected by Zika either locally or throughtravel to places where the virus is spreading. Another 38,303cases have been reported in U.S. territories, including PuertoRico.