Single-dose Zika vaccine can protect against infection

The first Zika vaccine with live virus has successfully protected mice against the infection after a just single dose, an advance that may improve the public health efforts to avoid the birth defects and diseases caused by the virus.
While a Zika infection typically results in mild or symptom-free infections in healthy adults and children, the risk of microcephaly and other diseases in the developing foetus is an alarming consequence that has created a worldwide health threat.
Pregnant women who are infected with the Zika virus but never display any disease symptoms may still give birth to a baby with microcephaly.

An effective vaccine is urgently needed for women of childbearing age and travellers to areas where the virus has been reported, researchers said.
Since Zika virus could also be sexually transmitted, prevention of men from infection through vaccination could also halt Zika transmission and diseases.
Rapid and promising progress has been made toward a Zika vaccine. These developing vaccines have been made from an inactivated version of the Zika virus or subunits of the virus; these vaccine candidates have been shown effective in mice and nonhuman primates.

"We chose to pursue a vaccine made from live virus that has been sufficiently attenuated, or weakened, to be safe, and is able to illicit robust immune response to protect us from Zika virus infection," said Pei-Yong Shi, professor at The University of Texas Medical Branch at Galveston (UTMB) in the US.

"Such live-attenuated vaccine has the advantage of single-dose immunisation, rapid and strong immune response and potentially long-lived protection," said Shi.
Researchers engineered the Zika virus by deleting one segment of the viral genome. A similar approach has successfully been used to develop a dengue virus vaccine, which is currently in phase three clinical trials.
The data indicated that the vaccine has a good balance between safety and efficacy, Shi said.
A single immunisation with the vaccine candidate produced strong immune responses and prevented the virus from infecting mice at all.
"Safety is a major hurdle when developing live-attenuated vaccine. Our Zika vaccine showed promising safety profile in mice when compared with clinically approved live-attenuated vaccines, such as the yellow fever vaccine," Shi said.

"Vaccines are an important tool for preventing Zika virus transmission and microcephaly," said Pedro F C Vasconcelos, director of Instituto Evandro Chagas at the Ministry of Health in Brazil.
"This vaccine, the first live-attenuated vaccine for Zika, will improve the public health efforts to avoid the birth defects and diseases caused by Zika in countries where the virus is commonly found," said Vasconcelos.
The research was published in the journal Nature Medicine.