Sanofi: Dengvaxia not guaranteed to prevent dengue

Sofia Tomacruz

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Sanofi: Dengvaxia not guaranteed to prevent dengue
(3rd UPDATE) However, when a person gets the vaccine after he has had an infection, the effectivity of the vaccine increases by up to 6 years, says Dr Ng Su Peing, global medical head of Sanofi

MANILA, Philippines (3rd UPDATE) – Days after it admitted attendant risks in its dengue vaccine, French pharmaceutical company Sanofi Pasteur said on Monday, December 4, Dengvaxia is not guaranteed to prevent dengue after all.

In a press conference, Dr Ng Su Peing, global medical head of Sanofi, said the vaccine is not recommended for those without prior infection.

The drug manufacturer sought to clarify that it released the vaccine commercially because clinical data at the time of licensing showed it was safe and effective. 

Sanofi representatives clarified, however, that continued tests over the years showed those who got the vaccine for preventive purposes – or those who had not been infected before – still faced the risk of getting severe dengue.

Dengvaxia “does not contain viruses that can make people ill with dengue or severe dengue,” Sanofi representatives said on Monday.  

What its clinical data showed is that there is risk of dengue before and after getting the vaccine. “Severe dengue observed in those who got the vaccine was not clinically different from those who had never been administered the shot.”

However, Peing explained, when a person gets the vaccine after he or she has had an infection, the effectivity of the vaccine increases by up to 6 years. But Dengvaxia increases the risk of contracting severe dengue for those who got the vaccine without prior infection.

This is why Peing said she would not recommend Dengvaxia for those who have not been infected with dengue. 

She said, however, that most Filipinos have already had prior infection since dengue is endemic in the Philippines. 

Increased effectivity, increased risk

“We noted at longer-term an increased risk of hospitalization and severe dengue in the vaccinated people without a prior dengue infection, compared to [the] placebo [participants],” Peing said. 

Follow-up study 5 years after the vaccine was administered showed an increase of 5 hospitalization dengue cases and 2 severe dengue cases for every 1,000 individuals who had been vaccinated and had had no prior infection. 

For those who were already infected with dengue, results showed a reduction of 15 hospitalization dengue cases and 4 severe dengue cases per 1,000 individuals who had been given the immunization shot.

Sanofi stressed that “all study participants who got severe dengue, whether vaccinated or not, have fully recovered.”

In a statement distributed to journalists on Monday, Sanofi said: “In individuals who have not been previously infected by dengue virus, there is an increased risk of hospitalization for dengue and severe dengue, predominantly Grade I or II Dengue Hemorrhagic Fever (DHF). Severe dengue can be categorized from milder to more severe forms as DHF I, II, III, and IV according to WHO.”

It stressed: “DHF IV was not seen in those vaccinated.”

It said it “shared this new data in full transparency with the FDA and DOH,” referring to the Food and Drug Administration and the Department of Health. 

Sanofi Pasteur is proposing an update to the vaccine label to reflect new data. 


Last Wednesday, November 29 – more than a year after its release of the world’s first dengue vaccine –  Sanofi advised the public that clinical studies revealed the vaccine poses more risks for recipients who had no prior infection. (READ: Dengue vaccine more risky for people without prior infection – Sanofi

In an update on its website at the time, Sanofi said: “The analysis confirmed that Dengvaxia provides persistent protective benefit against dengue fever in those who had prior infection. For those not previously infected by dengue virus, however, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection.” 

It added: “Vaccination should only be recommended when the potential benefits outweigh the potential risks (in countries with high burden of dengue disease). For individuals who have not been previously infected by dengue virus, vaccination should not be recommended.” 

The Philippine DOH, which purchased P3.5 billion worth of the vials in early 2016, said more than 700,000 Filipino youth have been given the vaccine under the government’s mass immunization program. It said 70,000 of them are at risk of more severe types of dengue in about two years after getting the vaccine.

As Sanofi was holding its press conference Monday, Justice Secretary Vitaliano Aguirre II said he had ordered the National Bureau of Investigation to probe Sanofi. Lawmakers are also set to investigate the DOH’s purchase of the vaccine.

The DOH has since suspended the P3.5-billion immunization program. 

Meanwhile, the FDA has also stopped the sale of Dengvaxia in the Philippine market until packaging labels are replaced to reflect the new warning.

The first dengue vaccine in the world, Dengvaxia provided protection from all 4 dengue strains. Previous recommendations stated healthy individuals aged 9 to 45 years old could be administered the shot in 3 doses at 6-month intervals.

The development of the vaccine was considered a major step in the prevention of dengue, with hopes that the drug could eventually help prevent millions of deaths. 

According to the World Health Organization, dengue is the fastest-spreading mosquito-borne disease. It is endemic in over 100 countries, putting 40% of the world’s population “living in an area at risk for dengue.”

Eleven countries, including the Philippines, approved the commercial release of Dengvaxia: Brazil, Costa Rica, El Salvador, Guatemala, Mexico, Paraguay, Peru, Indonesia, Singapore, and Thailand. –

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Sofia Tomacruz

Sofia Tomacruz covers defense and foreign affairs. Follow her on Twitter via @sofiatomacruz.