Vaccine for Zika virus may be years away, disease experts warn

A city worker fumigating a park in Santa Tecla, El Salvador, as part of preventive measures against the Zika virus.

(THE NEW YORK TIMES) As public health officials warn that the Zika virus is swiftly spreading across the Americas, the search is on to develop a vaccine to halt the disease, which could infect as many as four million people by the end of the year and has been linked to severebirth defects.

But even as a host of companies have announced plans to develop a vaccine, disease experts say it could be years — maybe as long as a decade — before an effective product makes its way to the public. Not only are scientists still learning about the virus, which until recently was viewed as relatively benign, but any vaccine must go through rigorous testing to ensure that it is safe and effective.

“It’s very important for people to be realistic,” said Dr. Jesse Goodman, a professor of medicine and infectious disease at Georgetown University, who between 2003 and 2009 was the director of the center at theFood and Drug Administrationthat approves vaccines. “It is a complex process, and for Zika, it hasn’t been on the map until this exploded inBrazil.”

Researchers are not only exploring ways to develop a vaccine but are also hoping to create a rapid test that would detect the presence of the virus’santibodies.

But for both the vaccine and test research, experts say most drug companies have been reluctant to invest in drugs or treatments for diseases in the developing world unless they see a financial reward.

Brazil has been grappling with the virus since the first case appeared in May 2015, and it has since spread to more than 20 other countries in the region, according to the World Health Organization, which onThursday rang an alarmabout the disease. Public health officials are particularly worried that Zika leads to a condition known asmicrocephaly, in which infants are born with abnormally small heads and damaged brains. Although researchers have not conclusively identified Zika as the cause, the number of babies born in Brazil with microcephaly has risen sharply along with the spread of the virus. Zika was first identified in 1947 in Uganda, but it rose to international attention in 2007, when an outbreak was identified in the Pacific islands.

Two major vaccine makers, the British company GlaxoSmithKline and Sanofi Pasteur, a French manufacturer, said this week that they were looking into the feasibility of developing a Zika vaccine by building on previous successes with other diseases.

GlaxoSmithKline developed a vaccine forEbola, which showed success in early clinical trials and is still being tested. Last year, Sanofi received approvals for the world’s first vaccine for dengue, which is closely related to Zika. However, Sanofi sounded a note of caution this week, even as it said it would look into a Zika vaccine. “There are too many unknowns about Zika to reliably judge the ability to research and develop a vaccine effectively at this time,” it said in a statement.

A handful of smaller companies have also said they are working on Zika vaccines, some on more aggressive timelines. One team, a collaboration between Inovio Pharmaceuticals, the South Korean company GeneOne Life Science and academic researchers in Canada and the United States, has said its product could beready for emergency useby this fall. Two other companies, Hawaii Biotech and the Protein Sciences Corporation, also announced plans for a Zika vaccine.

Meanwhile, public health officials said government researchers were working on at least two approaches to a vaccine and hoped to begin testing one of them in early clinical trials by the end of this year. That approach is a DNA vaccine method, which creates virus-like particles when it is placed into cells. The method was tried in a vaccine for West Nile, a related virus, and was found to be safe in early trials, but never progressed because theNational Institutes of Healthcouldn’t find a company willing to develop it further, said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases at the N.I.H.

Researchers will try the same approach with Zika by inserting a Zika gene into the same platform, in place of the West Nile gene. “I do not anticipate that we will have any problem partnering with pharmaceutical companies now,” he told reporters Thursday, referring to Zika.

Dr. Fauci added, however, “While these approaches are promising, it is important to understand that we will not have a widely available, safe and effective Zika vaccine this year and probably not even in the next few years.”

In a telephone interview Friday, Dr. Fauci said several factors could affect how long it would take for a vaccine to be approved, including how rampantly the disease spreads. A fast-moving disease, for example, would more quickly permit researchers to see if the vaccine is working.

Dr. Fauci said researchers were also eager to develop a rapid test to assess whether a person had been infected with Zika, to help pregnant women, in particular, find out if they have had the disease. A majority of people who are infected with Zika do not show any symptoms, and existing tests only seek out the active virus, which lasts in the body only for a short time. An easier-to-use test that looks for antibodies specific to Zika would be more useful, Dr. Fauci said, and he said academic researchers and some companies were exploring this avenue.

But even if the vaccine shows early success, drug companies — which have the capacity to manufacture large quantities of the product — must take an interest, he said, noting that earlier efforts to develop vaccines for West Nile andchikungunya, a related disease, have failed for lack of interest on the part of drug makers.

“It wasn’t perceived as a big economic boon for them to do that,” he said Friday.

Public health advocates have long criticized pharmaceutical companies for failing to invest in remedies for diseases that primarily afflict people in developing countries or ones that do not have a reliable market.

“What the private sector is most interested in are developing treatments for diseases that are known, common and predictable,” said Lawrence O. Gostin, a Georgetown law professor who co-wrote an article this week in themedical journal JAMAcalling on officials to aggressively combat Zika. He has called for more public-private partnerships to give pharmaceutical companies better incentives to develop treatments for neglected diseases.

“Most of these diseases are unpredictable,” he said. “They’re sporadic, often they flare up in poor countries, and then they go away.”

Others said the Zika outbreak should be a lesson to public health officials not to ignore low-profile diseases. “We need to have better tools for these diseases,” said Dr. Carolina Batista, the Latin America medical manager for the Drugs for Neglected Diseases initiative, who is based in Brazil. “We should not wait for the crisis to come and then start.”