To Dengue or Not to Dengue?

Jaydev Varsani – Clinical Pharmacist – Travel Lead

Understanding the Risk, the Vaccine, and Whether You Actually Need It

Dengue has quietly become one of the fastest-rising travel-related infections worldwide. Anyone heading to South Asia, Southeast Asia, South America, Central America, or parts of the Caribbean will have come across warnings about mosquito bites, rising case numbers, or that dreaded phrase: “dengue outbreak.”

At Murrays Chemist, we are seeing more travellers planning trips to regions where dengue is now considered endemic. Naturally, people ask the same question:

“Should I get the dengue vaccine before I travel?”

Let us break it all down properly.

What Exactly Is Dengue?

Dengue is a viral infection spread by the Aedes mosquito — mainly Aedes aegypti and Aedes albopictus. These mosquitoes bite during the day, which is why usual “dusk and dawn” malaria advice does not fully apply here.

There are four dengue virus serotypes. A person can be infected multiple times in their life because immunity to one serotype does not guarantee immunity to the others. The second infection is often where things get complicated.

Why Is Dengue a Problem?

Most people experience flu-like symptoms — fever, headache, joint pains, rash.

But a small proportion develop severe dengue, which can lead to:

• plasma leakage

• shock

• bleeding

• significant hospitalisation

• long-term complications

There is no specific antiviral treatment, so prevention is the main strategy: avoiding mosquito bites and, when appropriate, vaccination.

Enter Qdenga: The New Dengue Vaccine

Qdenga (TAK-003) is a relatively new vaccine licensed in the UK. It is a live attenuated vaccine, meaning it contains a weakened version of the virus that stimulates immunity without causing the disease.

It works by helping the body generate immune responses across different dengue serotypes. This reduces the risk of symptomatic infection and severe outcomes.

Dosing:
It requires two doses, given three months apart.
Long-term immunity is expected to be significantly stronger after completion of the two-dose course.

The SPC Position (Summary of Product Characteristics)

The SPC — the official licensing document — does not restrict Qdenga only to people who have had dengue previously.
It allows the vaccine to be used for individuals from 4 years of age, regardless of prior infection status.

So on paper, the licence permits vaccination of people with or without previous dengue.

However…

We practise in the UK, so we do not follow the SPC alone.

The JCVI and Green Book Recommendation

The UK’s Joint Committee on Vaccination and Immunisation (JCVI) and the Green Book (the gold-standard national immunisation guidance) take a more cautious stance.

Their position:
Qdenga should only be offered to individuals with a confirmed previous dengue infection AND who are still at high risk of repeat dengue exposure.

This excludes the majority of UK travellers.

Why Has the UK Adopted This Restrictive Approach?

It comes down to risk management and the well-known complexity of dengue immunity.

1. Secondary infection can be more severe than the first.
   If a vaccine triggers immunity that mimics a first infection, and the person later catches dengue in the endemic region, the illness could theoretically be more severe.

2. The JCVI is being extremely conservative with a new vaccine.
   Large global trials exist, but long-term real-world data in travellers remain limited.

3. The UK does not have dengue circulating.
   This makes our population “dengue naïve.”
   That increases the theoretical risk of severe dengue if immunity behaves unpredictably.

4. The UK prioritises safety when evidence is evolving.

So although other countries use Qdenga widely in naïve populations, the UK’s position is straightforward: vaccinate only if you have had dengue before.

So Should You Have the Dengue Vaccine?

This is where personal risk assessment comes in.

Ask yourself:

• Have you ever had dengue, confirmed by testing?

• Are you returning to a highly endemic area for work, family visits or long stays?

• Are you repeatedly exposed over many months or years?

• Are you comfortable following the JCVI’s restrictive guidance, which excludes most travellers?

For most UK travellers, the current answer is simple:

The vaccine is not recommended unless you have had dengue previously.

For those who have had dengue, Qdenga provides an important additional layer of protection before future exposure.

Final Thoughts: To Dengue or Not to Dengue?

The dengue vaccine world is evolving quickly. The product itself is promising and globally embraced, but UK guidance is deliberately cautious. At Murrays Chemist, we respect that — meaning we follow JCVI and Green Book recommendations strictly.

If you are travelling, the most important step is to understand your risk profile and consider whether vaccination is genuinely required or desirable based on your past medical history and travel pattern.

We can guide you through that assessment, explain the evidence, and help you make an informed decision.