Local authorities have launched a mosquito-control campaign across eight neighbourhoods in An Thoi, the island's worst-affected area.
Dengue infections have risen 6.9-fold year-on-year, with An Thoi reporting 672 cases, accounting for 65.11 per cent of the island's total.
Officials attributed the outbreak partly to alternating heavy rain and hot weather, which create breeding grounds for mosquitoes.
Population growth, tourism activities and the presence of more than 10,000 construction workers have also complicated disease prevention efforts.
The Long Chau vaccination centre on Phu Quoc reported that demand for dengue vaccine consultations and vaccinations had nearly doubled from the previous month.
Le Thi Giao Thi, a doctor with the Long Chau pharmacy and vaccination network, said the increase reflected growing public awareness of disease prevention.
Demand has risen particularly among adults working outdoors, children aged four and above, and people who have previously contracted dengue.
Long Chau said it had increased supplies of the Qdenga vaccine to meet demand, while maintaining cold-chain storage and pre-vaccination screening procedures.
Thi warned that dengue can occur year-round in Vietnam but typically increases during the rainy season, when standing water provides breeding sites for mosquitoes.
She urged residents to eliminate stagnant water, cover water containers, use mosquito nets and take precautions against mosquito bites.
Children and teenagers require particular attention because dengue can develop into serious complications, including shock, severe bleeding and organ failure.
Symptoms such as high fever, headache, body aches, nausea and rashes should prompt medical assessment, particularly in areas experiencing outbreaks.
Warning signs including persistent abdominal pain, repeated vomiting, bleeding, extreme fatigue, reduced urination or cold hands and feet require immediate medical attention.
Thi said the most dangerous phase often occurs between the third and seventh day of illness, even after a patient's fever has subsided.
In Vietnam, the Qdenga vaccine is approved for people aged four and above, with two doses administered three months apart.
The vaccine is designed to protect against all four dengue virus serotypes and reduce the risk of symptomatic illness and hospitalisation, although protection varies between serotypes.
Health experts stressed that vaccination does not provide complete protection and must be combined with mosquito control and the removal of breeding sites.
