PH, Mexico approve world’s first vaccine for dengue fever

INQUIRER FILE PHOTO

With the decision to approve the world’s first vaccine for dengue fever, the Philippines along with Mexico moves ahead of all other countries to address the spread of this mosquito-borne disease.

The World Health Organization (WHO) is still unclear how long the tetravalent dengue vaccine called Dengvaxia would protect those who received it and at the same time, its maker Sanofi Pasteur, is yet to announce how much the vaccine will cost.

The Philippines’ quick approval was necessary. From January through Nov. 21, 2015, a total of 169,435 suspected cases of dengue, including 511 deaths were already recorded by the Department of Health’s Epidemiology Bureau. This is 59.5 percent higher compared with the same reporting period in 2014 (106,241 cases).

The Philippines was just one of several Southeast Asian countries that reported large numbers of cases in 2015. The others were Thailand with 107,000 as of Nov. 8 and Malaysia with 111,285 cases as of Dec. 5.

Fast-growing disease

The number of cases in the world has risen thirty-fold over the last 50 years, according to the WHO, making dengue the world’s fastest-growing mosquito-borne disease, which leaves more than half of the world’s population potentially at risk.

The vast majority, about 80 percent, of people infected with dengue virus are asymptomatic or have only mild symptoms such as an uncomplicated fever.

About 5 percent of infections cause more severe illness, and less are life-threatening.

At least five other dengue vaccines are in clinical development.

Most severe form

The WHO says that half a million people are hospitalized by the illness every year, many of them children of which around 2.5 percent die. The most severe form of the disease, dengue hemorrhagic fever, accounts for 1 percent of cases, killing 22,000 people a year, the  WHO says. It results in bleeding and blood plasma leakage. It can be fatal, in particular among children.

The WHO estimates that half of the world’s population is at risk from dengue. Its symptoms include fever, joint pain and vomiting, which can become lethal.

Dengvaxia from Sanofi’s vaccines division, Sanofi Pasteur, protects against all four dengue virus serotypes and will be aimed at residents aged 9 to 45 in endemic areas.

The vaccine has undergone testing on more than 29,000 patients worldwide.

Although this does not cover very young children, who are often most vulnerable to the disease, Sanofi chief executive Olivier Brandicourt hailed the approval as “a historic milestone for our company, for the global public health community and, most importantly, for half the world’s population who live at risk of dengue.”

In the tests Sanofi conducted, the vaccine was administered in three doses spaced out over a year.

“The vaccine actually is given in three dose schedules with a six-month interval. It is being given (to people) from 9 years up to 45 years of age. This is the age range wherein most of the dengue cases are being reported, particularly in endemic countries here in Asia,” according to Dr. Joselito Santa Ana,  Sanofi Pasteur head of dengue vaccine operations in the region.

Average rate of efficacy

According to a WHO report published in late 2014, the vaccine had an average rate of effectiveness of about 60.8 percent in protecting against the four strains of dengue currently circulating.

Sanofi said its vaccine was shown to “reduce dengue due to all four serotypes [strains] in two-thirds of the participants,” a figure similar to the 65.6 percent rate reported in a study published in September by the New England Journal of Medicine.

That is relatively low for a vaccine. Common vaccines like those for measles and polio are more than 95-percent effective.

But Dengvaxia appeared to be particularly effective in protecting people from the most extreme, potentially life-threatening form of the disease, known as dengue hemorrhagic fever, which can cause internal bleeding, shock, organ failure and death.

Sanofi said in its statement that the drug “prevented 9 out of 10 cases of severe dengue and 8 out of 10 hospitalizations due to dengue.”

Cameron Simmons, a professor of microbiology and immunology at the University of Melbourne, told Al Jazeera that the vaccine must be widely used in order to significantly curb the number of dengue cases, but noted that it will not fully eradicate the virus.

“The evidence from the vaccine trials is that it can prevent hospitalization for about 80 percent of those who get vaccinated,” he said.

“It would need to be very widely used in order to result in a major reduction in the prevalence of dengue,” he added.

Reducing dengue deaths

The vaccine’s maker is hailing it as an important tool to reach the WHO objective on dengue, a potentially deadly disease for which children are at particular risk.

“Together with vector control, it will form an integrated approach in reducing dengue mortality by 50 percent and reducing the dengue morbidity by more than 25 percent by 2020,” Dr. Santa Ana, speaking from Manila, told VOA on Wednesday.

Clinical tests were carried out on 40,000 people from 15 countries.

Some two-thirds of those over the age of 9 were deemed to be protected and the vaccine was found to be 93 percent effective against the most severe form of disease, dengue hemorrhagic fever.

Long-term efficacy

While being hailed as a breakthrough, there is concern about vaccinating younger children and an unanswered question about the new vaccine’s long-term efficacy.

A higher incidence of hospitalization in the third year after vaccination among children younger than 9 years of age naturally infected with dengue raises a “critical question” whether this is a short-term or long-term phenomenon,” noted an editorial in the Sept. 24 edition of the New England Journal of Medicine which suggested booster doses of the vaccine might reduce this risk.

The journal praised the trials as “superbly conducted” while noting, due to traditional concerns about partial, waning immunities the “bumpy road to a vaccine-based solution for dengue continues.”

“As with all new vaccines, it is unknown how long the measured protection against dengue will last,” the WHO also cautioned in November 2014.

Pharmaceutical companies in Japan, Britain and the United States are also developing dengue vaccines.

Vaccine development

The CYD-TDV vaccine, in development for 25 years, has been submitted for licensing in 18 other countries in Asia and Latin America where dengue is endemic.

India may exempt Dengvaxia from large-scale clinical trials in order to expedite clinical trials, the Economic Times reported Tuesday, quoting health industry sources.

More than 90,000 dengue cases with 181 deaths were reported in India through the end of November for this year.

Dengue was traditionally a disease primarily confined to the tropics. Now, about half of the world’s population is considered at risk due to urbanization, jet travel and climate change.

Dengue cases have soared thirty-fold in the last half century, according to the WHO, with an estimated 400 million people now infected annually.

The first doses of Dengvaxia, which utilizes a yellow fever virus with substitutions of two genes encoding dengue proteins, are already being produced in France where manufacturing of 100 million doses annually are planned, according to Sanofi Pasteur.