Scientists take big step closer to creating 2 vaccines against Zika

Just five months after the Zika virus was declared a global public health emergency, a scientific team’s feverish efforts to create a vaccine against the viral threat have borne promising fruit: With a single shot of two different types of vaccine, experimental mice gained neartotal immunity to Zika for at least two months.

Writing in the journal Nature on Tuesday, a U.S.Brazilian team of scientists reported that two distinct vaccine candidates conferred powerful protection from Zika infection when they were delivered by injection to mice.

“We were very surprised — and quite impressed — that a single shot of either of these vaccines provided complete protection,” said study co-author Dr. Dan H. Barouch, who after years of work on vaccines against HIV pivoted in late January to work on Zika.

“Of course, we need to be cautious about extrapolating” from a study that has so far only shown success in mice, said Barouch, who directs vaccine research at Beth Israel Deaconess Medical Center in Boston.

But several of the study’s findings “certainly raise optimism that the development of a safe and effective vaccine against Zika virus for humans may be successful,” he added.

The Zika vaccine effort is a race against time. Since its arrival in Brazil in 2013, the Zika virus has marched steadily north. Carried by the Aedes aegypti mosquito, the virus is already spreading vigorously in Puerto Rico and is expected to circulate inside the U.S. this summer.

The Centers for Disease Control and Prevention has concluded that Zika infection in pregnant women is the cause of brain abnormalities in their infants. For those who are not pregnant, Zika infection is generally not dangerous. But it can, in rare cases, cause Guillain-Barre syndrome, a life-threatening condition in which the immune system attacks the peripheral nervous system, causing partial paralysis that is generally temporary.

The team also discerned how the tested vaccines worked to provide protection — an important milestone in building a vaccine. Soon after their first shot, the immune systems of lab mice quickly mounted an army of circulating antibodies that recognized and attacked Zika virus as soon as it began replicating.

Such “antibody protection,” produced by the immune system’s B-cells, is not generally as enduring as the long-term immune memory produced by T-cells. But “it’s good: it makes a vaccine that’s nice and neat and simple,” said Dr. Anthony Fauci, director of the National Institute for Allergies and Infectious Diseases.

Fauci called the vaccine candidates’ early success “an important step on the road to getting vaccines into humans.” He confirmed that several other Zika vaccine candidates are being tested in animals, and that very early testing in humans could begin as early as late August.