Misconceptions about Dengue fever: Latest prevention recommendations for the whole family

Important insights were shared by leading experts at the scientific seminar Addressing misconceptions about Dengue fever and protecting the whole family held on March 26, 2026 at Tam Anh General Hospital Hanoi. The event was organized by Tam Anh Research Institute in collaboration with the Tam Anh General Hospital Group, with technical support from Takeda Vietnam.

Dengue fever (Dengue Hemorrhagic Fever – DHF) is the second-largest public health challenge among infectious diseases in Vietnam, after influenza, with a mortality risk of up to 20% if not treated promptly, even in young, otherwise healthy individuals. When compared with vaccine-preventable diseases such as meningococcal disease, the incidence of DHF is more than 10,000 times higher. Experts warn that the public should closely monitor for abnormal signs, seek timely medical care, and proactively prevent the disease early through vaccination combined with other routine measures.

DHF continues to be a serious public health burden in Vietnam, as the number of cases shows an increasing trend and the disease course becomes increasingly unpredictable. According to data from the National Institute of Hygiene and Epidemiology (NIHE), the northern region has recently recorded a significant rise in cases, not only among children but across all age groups, including adults and the elderly.

Dr. Nguyen Trung Cap, MD, Specialist level II – Deputy Director of the National Hospital of Tropical Diseases stated that at his workplace, famously known as Vietnam’s leading center for infectious disease treatment, DHF has consistently been one of the leading causes of hospitalization. In 2024 alone, the hospital admitted 2,123 inpatient cases. Although most patients recovered, 43 cases progressed to severe outcomes, resulting in discharge against medical advice or death. These figures underscore the concerning severity of DHF compared with other common infectious diseases such as influenza or pneumonia.

According to Dr. Nguyen Trung Cap, DHF has an unpredictable course and can deteriorate within hours. Based on professional guidelines from the World Health Organization (WHO), DHF is classified into three severity levels: (1) without warning signs, (2) with warning signs, and (3) severe DHF. However, a key concern is that the disease may initially present with common symptoms such as high fever, headache, myalgia, and rash, but can rapidly progress to a critical stage without clear prior indications.

For this reason, the most common misconception among the public today is the belief that fever subsiding means recovery. Up to 84% of cases may not present clear clinical symptoms, yet individuals can still serve as significant sources of transmission within the community through Aedes mosquitoes.

Clinical practice has recorded many cases with rapid and severe progression. For example, a 14-year-old male patient with obesity was initially diagnosed with DHF and discharged for home monitoring. Within a few days, he developed hypotension, progressed to severe shock, and died after eight days of treatment.

Dr. Nguyen Trung Cap noted that data from the NIHE show a recent surge in DHF cases in northern Vietnam. Photo: Tam Anh Research Institute.

For this reason, the most common misconception among the public today is the belief that fever subsiding means recovery. Up to 84% of cases may not present clear clinical symptoms, yet individuals can still serve as significant sources of transmission within the community through Aedes mosquitoes.

Clinical practice has recorded many cases with rapid and severe progression. For example, a 14-year-old male patient with obesity was initially diagnosed with DHF and discharged for home monitoring. Within a few days, he developed hypotension, progressed to severe shock, and died after eight days of treatment.

Not only children, but also young, otherwise healthy individuals may face similar risks. A 20-year-old female student diagnosed with DHF and treated at home during the early days developed abnormalities by day 4, including coma, hypotension, severe liver failure, and renal failure, and subsequently died despite intensive resuscitation.

Dr. Nguyen Trung Cap noted that children have a nearly threefold higher risk of shock compared with adults. Statistics indicate that among every 4 – 5 pediatric hospitalizations for DHF, one case may progress to life-threatening shock. The main reason is that children have higher vascular permeability than adults, leading to rapid plasma leakage and decreased circulating volume. This complication typically occurs on days 4 or 5 of illness, with warning signs such as lethargy, restlessness, or cold extremities.

This risk is particularly severe among overweight or obese children, who have a 59% higher risk of progressing to shock compared with children of normal weight. Physiological changes associated with fat accumulation and chronic inflammation make obese children more susceptible to a cytokine storm and severe vascular damage when infected.

Given the unpredictable course of the disease, patient monitoring must be continuous and cautious. In the early stage, patients may present only with fever accompanied by vomiting, rash, or muscle pain. However, when warning signs appear, such as severe abdominal pain, persistent vomiting, mucosal bleeding, lethargy, fluid accumulation like pleural effusion, ascites, rapidly rising hematocrit with declining platelet count, the disease has entered a critical phase, with risks of plasma leakage, shock, respiratory failure, and multi-organ failure, Dr.  Nguyen Trung Cap emphasized.

In severe cases, DHF causes plasma leakage leading to shock, severe bleeding, and multi-organ failure. Multiple organs may be affected simultaneously, including elevated liver enzymes, liver failure, acute renal failure, myocarditis, pulmonary edema, respiratory failure, encephalopathy, severe thrombocytopenia, and cytokine storm. This is why WHO and the Ministry of Health emphasize that DHF requires close monitoring and should not be managed casually at home.

Older adults with underlying conditions are also at particularly high risk of severe complications due to increased vascular permeability and exaggerated inflammatory responses, which accelerate organ damage. In clinical practice, Dr. Nguyen Trung Cap described a case of a 51-year-old male patient in Hanoi with multiple chronic conditions, including diabetes and hypertension, who was admitted in severe shock with multi-organ failure. Despite intensive treatment, his liver failure and respiratory failure continued to worsen.

Studies show that chronic diseases significantly increase the risk of severe DHF progression: highest in patients with kidney disease – 4.54-fold increase, followed by patients with obesity/overweight – 3.41-fold, patients with diabetes – 3.39-fold, patients with cardiovascular disease – 2.71-fold, and patients with hypertension – 2.19-fold, Dr. Nguyen Trung Cap emphasized.

The risk increases even more sharply when comorbidities coexist: eightfold in patients with both diabetes and cardiovascular disease, nearly sixfold with cardiovascular disease and dyslipidemia, and 4.25-fold with diabetes and dyslipidemia. Therefore, physicians recommend that individuals with underlying conditions, especially those over 60 years of age, should be hospitalized for close monitoring immediately upon infection and must not self-treat at home.

Conversely, even patients who survive critical illness often face substantial treatment time and costs. A 61-year-old female patient with diabetes required 63 days of intensive care, including 50 days of mechanical ventilation and approximately 30 days of dialysis, with total costs exceeding VND 1.3 billion before discharge. Beyond direct medical expenses, patients may also experience indirect costs and long-term sequelae such as hair loss, blurred vision, and reduced concentration, affecting daily life and family finances.

According to Dr. Bach Thi Chinh, MD, Specialist level I – Medical Director of the VNVC Vaccination System, one of the major barriers to DHF prevention lies not only in disease risk but also in public perception. Many people still believe DHF is seasonal, that treatment is sufficient once infected, or that vaccination is unnecessary when healthy. Concerns about vaccine safety, vaccination costs, and insufficient counseling from healthcare providers also lead many families to delay preventive decisions.

Therefore, Dr. Bach Thi Chinh emphasized that healthcare professionals play a crucial role in changing awareness and preventive behavior. When people are provided with clear information about infection risk, disease severity, and the benefits of vaccination, and are fully informed that post-vaccination reactions are generally mild and transient, confidence in vaccines will be strengthened and vaccination uptake will occur earlier.

In the context of widespread DHF circulation and unpredictable progression, vaccination is considered the most proactive and sustainable preventive measure. The DHF vaccine Qdenga, developed by Takeda Japan, has been approved in multiple countries and prequalified by WHO for quality, safety, and efficacy. In Vietnam, the vaccine has been licensed since 2024 for individuals aged 4 years and older, administered in a two-dose schedule spaced three months apart. Clinical trial data show that the vaccine reduces the risk of infection by approximately 80% and the risk of hospitalization or severe disease by more than 90%.

Dr. Bach Thi Chinh highlighted that clinical and real-world data demonstrate that the vaccine significantly reduces infection risk, particularly lowering hospitalization and severe complication rates. WHO included the vaccine in its prequalification list in 2024, and many countries have implemented widespread vaccination with a favorable safety profile. Photo: Tam Anh Research Institute.

In addition to awareness barriers, cost is another factor influencing vaccination decisions. In Vietnam, the minimum cost of hospitalization for DHF monitoring is approximately VND 10 million per episode and may increase to VND 120 – 720 million for severe cases, whereas the cost of a full vaccination course of two doses is only around VND 2.5 – 2.8 million. This disparity shows that early prevention not only protects health but also significantly reduces financial burden.

Accordingly, medical associations now consistently recommend proactive DHF vaccination for all individuals aged 4 years and older within the family. Pre-vaccination testing is not required; however, individuals should follow the official usage guidelines approved by the Ministry of Health on May 14, 2024.

Dr. Nguyen Nhu Dien – Medical Manager of the VNVC Vaccination System further noted that despite the availability of specific preventive measures, many people remain hesitant due to misconceptions such as the disease being not dangerous, affecting only children, or the vaccine being new and unsafe. He emphasized that these views do not reflect current epidemiological realities. DHF is increasingly affecting adults, progresses more severely in individuals with underlying conditions, and may leave long-term sequelae. Meanwhile, the vaccine has undergone extensive research, long-term monitoring, and has been used in multiple countries with well-established safety data.

Dr. Nguyen Nhu Dien shared common situations, misconceptions, and hesitation among the public regarding DHF fever and DHF vaccination, noting that these are mainly due to an incomplete understanding of disease risk, vaccine effectiveness, and safety. Photo: Tam Anh Research Institute.

Therefore, Dr. Nguyen Nhu Dien recommends that all individuals act early to protect their families from a dangerous disease, unpredictable in progression, rapidly evolving, and with a high risk of mortality, yet preventable through vaccination. He advises the public to proactively monitor their health when experiencing fever, avoid prolonged self-treatment at home, and seek medical care immediately upon the appearance of warning signs. In particular, mosquito control and elimination of breeding sites should be combined with vaccination for effective prevention.