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Foundation note: The immunisation programme and how vaccines are made

Dengue vaccines: Qdenga, DengiAll and antibody dependent enhancement

Prelims and Mains

LeadIndia's first dengue vaccineJuly 2026

Why in news

The Central Drugs Standard Control Organisation granted marketing authorisation to Qdenga in July 2026, the first dengue vaccine approved in India, for people aged 4 to 60.

Background

Dengue is a viral disease spread by the Aedes aegypti mosquito, which bites by day and breeds in clean standing water.
The virus has four serotypes, DENV-1 to DENV-4. Infection with one gives lasting protection against that one, and only brief protection against the others.

A second infection by a different serotype is often more severe than the first.
India carries close to a third of the world's dengue burden.

Why dengue vaccines are hard to make

Antibodies from a first infection can help a different serotype enter cells in a second infection. This is antibody dependent enhancement.

So a vaccine must protect against all four serotypes equally. Partial protection can leave a person worse off than no vaccine.
An earlier vaccine could be given safely only to people who had already had dengue, which meant testing before vaccination.

The vaccine

Qdenga is a live attenuated tetravalent vaccine, built on a dengue type 2 backbone.

It is given as two doses, three months apart, and needs no test for earlier infection.
In trials it was about 80 per cent effective against confirmed dengue and about 90 per cent against hospitalisation.
The caveat: in people who have never had dengue, protection is shown only against DENV-1 and DENV-2, which raises a concern about later disease from DENV-3.
It is not part of the Universal Immunisation Programme.

All four serotypes, together

A national study found all four serotypes circulating together in eight States and Union Territories, a state called hyperendemicity.

DENV-2 was the most common.
About 7 per cent of patients carried two or more serotypes at once, and were more likely to develop severe dengue.
Which serotype circulates decides how well the vaccine works, so surveillance has to continue alongside it.

The way forward

Keep serotype surveillance running, and watch vaccinated children for later severe disease.
Decide on a public programme only with Indian data on safety in those never infected.
Continue mosquito control, since no vaccine removes the need for it.
Support the indigenous vaccine candidates now in trials.

Prelims facts

Dengue has four serotypes; the vector is Aedes aegypti.
Qdenga: live attenuated, tetravalent, two doses, ages 4 to 60, no test before vaccination.
It is built on a DENV-2 backbone.
Approval in India comes from the Central Drugs Standard Control Organisation.

Open the lead on its own page

Dengue has four serotypes, and antibodies from a first infection can help a different serotype enter cells in a second, which is antibody dependent enhancement and is why dengue vaccines are hard to design: vaccination raises type specific antibodies, which block one serotype, and cross reactive antibodies, which block all four only at high levels and can enhance a new infection into severe dengue once they wane. Qdenga (TAK-003), made by Takeda, is a live attenuated tetravalent vaccine on a dengue type 2 backbone, given as two doses three months apart to people aged 4 to 60 with no test for earlier infection; in July 2026 it became the first dengue vaccine approved in India, outside the Universal Immunisation Programme. DengiAll, by Panacea Biotec with the Indian Council of Medical Research (ICMR), is a physical mix of four weakened serotypes derived from US National Institutes of Health candidates, closely similar to Brazil's Butantan DV, and completed phase 3 enrolment of 10,335 volunteers in January 2026 with two years of follow up before approval.

Antibody dependent enhancement

Vaccination
The vaccine raises type specific and cross reactive antibodies
Cross reactive antibodies
They block all four serotypes only while their levels are high
Levels wane
Over time the cross reactive antibodies fall to low levels
New infection enhanced
Low levels help a new dengue infection instead of blocking it
Severe dengue
The enhanced infection can turn into severe dengue

A vaccine that leaves only waning cross reactive antibodies can make a later dengue infection worse rather than milder.Source: The Hindu, 15 June 2026

What changed

21 Jul 2026LeadIndia's first dengue vaccine