MANILA - The Department of Health is spending 3 billion pesos for the purchase of the newly discovered dengue vaccine but not everyone can use it to prevent infection.

Health Secretary Janette Garin said the vaccine, discovered by drug company Sanofi Pasteur, is recommended only for people ages 9 to 45 years old.

"We don't recommend it [for above 50 years old] because there would be other interactions. You would've been exposed to many diseases. The safety has not been established that well if you inject it above 45 years old. That is why we want to play on the safe side," she said in an ANC Headstart interview.

"The vaccine is a live virus that has been killed so you don't know the reaction of the person if you're above 45 years old. What was established in the study was the safety,the efficacy for 9-45 years old. If you look at the strategy of implementing it especially if you talk about the government, it should best be given to Grade 4 or Grade 5 students, 9-10 years old, kasi sila yung malaki ang volume. And if they're protected because the seniors and the adults get it from the children so kung hindi na nai-infect ang mga bata, wala na ring source."

Garin said the DOH cannot reveal the unit price of the dengue vaccine because there could be comparisons from the private sector. She added they were given a 34 percent discount by the manufacturer.

The health secretary said most dengue cases in the country are found in the National Capital Region, Region III and Region IV-A.

She said the Philippines is already spending 16 billion pesos on dengue treatments yearly.

Last month, the Philippines became the first Asian country to approve the sale of the world's first-ever dengue vaccine.

The dengue vaccine is expected to arrive in the country next week for the private sector.

The World Health Organization says as many as 400 million people are infected worldwide every year, and two-thirds are in Asia.

Scientists have long been stumped by dengue, which has four separate strains, forcing researchers to find a drug able to fight all of them at once.

Clinical tests -- carried out on 40,000 people from 15 countries -- have found Dengvaxia can immunize two-thirds of people aged nine years and older, rising to 93 percent for the more severe form of the disease, dengue haemorrhagic fever.

It was also found to reduce the risk of hospitalization by 80 percent.

Dengue can trigger a crippling fever, along with muscle and joint pain. There is no known cure, and children are at particular risk.

The deadliest form of the disease kills 22,000 people a year, the WHO says.

It was once considered a disease of the tropics, endemic in only nine countries, but globalization, urbanization, climate change and jet travel are helping it to move into more temperate zones.

It is now endemic in more than 100 countries.

The WHO says cases have risen 30-fold over the last 50 years, with more than half the world's population potentially at risk. With Agence France-Presse