Scientists predict Zika virus will become part of the new normal for Americans, requiring routine vaccinations.
Once Zika virus arrives in the United States, it will be here to stay. Leading experts now predict that the mosquito-borne disease will become a constant low-level threat that Americans will need to be vaccinated against routinely—as we do now for rubella, a virus that, like Zika, causes birth defects.
That is, once there is a vaccine for Zika. The earliest possible deployment of Zika vaccines could be several years away, researchers from around the globe predicted at an Atlanta conference Tuesday, the annual meeting of the Global Virus Network.
Overall, they said, Zika should be understood not as an epidemic wave that will pass over the world and then vanish, but rather as a permanent problem that will wax and wane, as West Nile virus has.
“We don’t know the future course of the epidemic of Zika, but we have to be prepared for the virus to be present for years,” José Esparza of the University of Maryland School of Medicine, current president of the Global Virus Network, said at the conference. “Without a vaccine, we will not be able to control the future course of this epidemic.”
Race for a Vaccine
Everyone reluctantly accepts that vaccines will take some time, while also expecting that infections could reach the United States soon. “The risk of Zika virus beginning to circulate in the United States on the mainland—it’s already in Puerto Rico, of course—is going to be peaking during the next few weeks,” said Scott Weaver, a virologist from the University of Texas Medical Branch.
“The number of travelers coming into the U.S. with Zika is very high, the temperatures are permissive now for mosquito transmission, and populations of mosquitos are growing,” he said.
A vaccine is most needed to protect women who are pregnant or planning to be, because the virus causes devastating birth defects that seem to appear late in pregnancy, and may also cause more subtle problems as children get older.
“We have no information to believe there are any long-term consequences from infection to healthy adults or healthy children,” Weaver said.
While a small vaccine trial sponsored by the National Institutes of Health could begin as early as next fall, expanding that research into trials with thousands of participants could be complicated by the rapid growth of the epidemic, which is both infecting people and also rendering them immune once they recover.
The first Zika vaccines to be developed probably won’t go to everyone, Weaver predicted. “I think initially there will be some vaccines developed and licensed that are not optimal for vaccinating large populations, that will require multiple doses,” he said. “Those will probably be targeted to girls before they reach childbearing age, or women … if we can determine that they are not immune, if we have the diagnostics to do that.
“And then eventually we should be able to develop a live attenuated vaccine, like the one we have now for yellow fever that has been available for many decades in South America,” Weaver said. Then, he added, doctors can vaccinate children, and the population will develop what we think of as “herd” immunity that protects even the unvaccinated.