New dengue vaccine

Dengue fever is an endemic disease of Thailand with continuous outbreaks. The situation of dengue outbreaks tends to increase. Data from the disease surveillance system, Bureau of Epidemiology, Department of Disease Control found that the number of patients increased 3 times in the same period. In addition, there were reports of patients who died from dengue fever as many as 33 people, which is a concerning number. This makes us should be aware of the importance of this disease because although it is a common disease and some patients may have non-severe symptoms, in some patients it may be severe to the point of causing death.

What causes dengue fever?

Dengue fever is caused by infection with a virus called “dengue virus (dengue virus; DENV)” which has 4 serotypes Dengue 1 (DEN1), Dengue 2 (DEN2), Dengue 3 (DEN3), and Dengue 4 (DEN4). If infected with any one serotype, the body will have immunity to that dengue virus serotype for life, but will not have immunity to other serotypes. Therefore, it is possible to be infected with other serotypes and become ill with dengue fever if infected later.

Who can get dengue fever?

Infection and illness with dengue fever can be found in all age groups, from young children to the elderly. The symptoms vary according to the infecting serotype and the strength and health of the infected person. The highest number of dengue patients is found in children aged 5–14 years. However, from data over the past 20 years, it was found that the trend of disease occurrence in adolescents and adults aged 15 years and older has increased.

Dengue infection in adults is increasing and more dangerous

As mentioned above, in the past 20 years, the trend of disease occurrence in adolescents and adults has increased, while pediatric patients under 15 years old have a decreasing trend. The mortality rate in adults is higher than in children. It was found that the mortality rate in adults aged 25 years and older is 2–3 times higher than in children aged 5–24 years. Factors that increase the risk of death in adults include having chronic underlying diseases and others such as:

• Obesity

• Diabetes

• Hypertension

• Liver and kidney diseases

• Chronic alcoholism

• Asthma

• Chronic obstructive pulmonary disease

• Late hospital visit

• Self-medication such as drug sets, NSAIDs pain relievers which cause severe bleeding

Symptoms of dengue fever

As known, dengue fever is caused by infection with dengue virus which has 4 serotypes. From being bitten by an infected Aedes mosquito, a person can be infected with dengue more than once with different serotypes from the first infection. Thailand has outbreaks of all 4 serotypes circulating alternately depending on the period, but serotypes 1 and 2 are the most common. The severity of dengue fever varies among individuals. The first infection is mostly not severe, and the body will have immunity to that serotype for life. However, the second infection from a different serotype may be more severe.

Symptoms of dengue fever in the initial phase

• Sudden high fever, fever higher than 38.5 degrees

• Headache

• Retro-orbital pain

• Muscle aches

• Nausea, vomiting

• May have bleeding spots on arms, legs, trunk, nosebleed, bleeding from gums

Symptoms of dengue fever on days 3–7 of illness

May have severe symptoms

• Shock

• Severe abnormal bleeding

• May die

Prevention of dengue fever

The best prevention of dengue fever is to prevent mosquito bites, including eliminating mosquito breeding sources around the house.

Dengue vaccination is another method that helps prevent dengue fever and reduce severity. Currently, there are 2 dengue vaccines registered in Thailand which can prevent all 4 dengue serotypes.

The first vaccine (Dengvaxia®) has been used in Thailand since 2017. It is a live attenuated vaccine, provides good protection against serotypes 3 and 4, and moderate protection against serotypes 1 and 2. It has overall efficacy of 65% and prevents hospitalization from dengue by 80%. It is given in 3 doses, each dose 6 months apart. It can be given in people aged 6–45 years who have had dengue before only, because it was found that if given in people who have never been infected before, there is a risk of increased severity.

The second dengue vaccine, which is a new vaccine (QDenga®), was registered for use in Thailand in 2023, which can provide good protection against serotypes 1 and 2.

Information of the new dengue vaccine

The second dengue vaccine or QDenga® has been used in 16 countries worldwide. It is a live attenuated vaccine that can provide good protection against serotypes 1 and 2, which are the most common in Thailand.

Advantages of the new dengue vaccine

• Has overall efficacy of 80%

• Prevents hospitalization from dengue up to 90%

• Can be given in people aged 4 years and older

• Can be given in both people who have had and never had dengue before

• No need for blood test for dengue immunity before vaccination

How is the new dengue vaccine given?

This new vaccine requires 2 doses, administered subcutaneously （subcutaneous）, with an interval of 3 months from the first dose

Contraindications for the new dengue vaccine

People with immunodeficiency patients using immunosuppressive drugs, cancer patients receiving chemotherapy, HIV patients, etc.

Pregnant and breastfeeding women. It is recommended that women of reproductive age use contraception for at least 1 month after vaccination. However, a doctor should be consulted before receiving the vaccine

People with a history of severe allergy to vaccine components

Safety and side effects of the vaccine

The vaccine is safe. Most side effects are common symptoms after vaccination, occurring within 2 days after injection and resolving on their own within 3–4 days. Follow-up at 4.5 years after vaccination did not find increased severe dengue illness in those vaccinated who had never been infected before. Side effects that may be found

• Pain, swelling, redness, heat at injection site

• Fever, muscle aches

• Headache

What is the long-term efficacy? Is a booster needed?

Follow-up at 4.5 years after vaccination found that efficacy decreased to 61% for prevention of dengue, but still could prevent hospitalization from dengue at a high level, which is 80%

However, there is still no data after 4.5 years and no recommendation for booster dose. Further study results are needed

If previously infected with dengue, can vaccination be given? How long after recovery?

Because second dengue infection is often more severe, those who have been infected are recommended to receive vaccination to prevent severity in the next infection, by receiving vaccination at least 6 months after recovery

If previously received the old dengue vaccine, can the new vaccine be given?

There is still no data on giving the new vaccine in people who previously received the old vaccine, both in those who completed or did not complete the vaccination and want to continue. However, a doctor should be consulted before vaccination for efficacy and safety

Summary

Dengue fever is a disease that has outbreaks in Thailand every year, especially during the rainy season. From statistics, patients are found from childhood to the elderly, and recently there has been a significant increase in adult cases, some of which are severe and lead to death

Currently, vaccines have been developed for prevention of dengue. At the end of 2023, a new dengue vaccine was registered that can provide good protection against serotypes 1 and 2, which are commonly found in Thailand. It can prevent hospitalization from dengue up to 90% and can be given in both those who have had and never had dengue before. It is a safe vaccine, therefore it is another option for dengue prevention. However, a doctor should be consulted before receiving vaccination for efficacy and safety

Consult a specialist doctor with Praram 9 V. Consult a doctor anywhere via video call （Telemedicine）