Dengue Vaccine Offers Lessons But Where Do We Go From Here?
Darin Seehafer
Darin Seehafer
Sr. Director, Center for Vaccines and Emerging Infectious Diseases

Dengue virus, a mosquito-borne flavivirus, has rapidly spread around the globe. According to the World Health Organization, it is now widespread throughout the tropics. Regional risk variations are influenced by rainfall, temperature, and unplanned rapid urbanization. This increasing threat has many pharmaceutical companies scrambling to license a vaccine that might stem the tide of infection.

Dengvaxia, made by Sanofi Pasteur, is one such vaccine. However, the vaccine has faced challenges in the Philippines. As part of its national immunization program, approximately 730,000 students were vaccinated with Dengvaxia in 2016 but there are now concerns that the vaccination has left some at risk to more severe disease upon reinfection. Sanofi Pasteur acknowledged the finding in an announcement in late 2017:

Sanofi Pastuer Press Release

Nov. 29, 2017 - Based on up to six years of clinical data, the new analysis evaluated long-term safety and efficacy of Dengvaxia in people who had been infected with dengue prior to vaccination and those who had not. 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.

Following Sanofi Pasteur’s announcement, the Philippine’s Department of Health (DOH) stopped the Dengue immunization program and called for a refund of all the money spent on the vaccine. Currently, the Philippines DOH and Sanofi Pasteur are at odds as to what is appropriate with regard to compensation.

Meanwhile, a larger issue has been raised by both the Philippine Congress and Justice Department, regarding the way the vaccine was added to formulary and eventually purchased. Unfortunately, sorting this all out has become a bureaucratic blame game as the past and present Philippine Presidential administrations rebuke each other.

Compounding matters, the withdrawal of the vaccine and the ensuing controversy has started to erode parent confidence in immunizations in the Philippines. To allay fears, 58 doctors (Doctors for Truth) signed their name to a statement calling for an end to the rhetoric and misinformation:

"The unnecessary fear and panic, largely brought about by the imprudent language and unsubstantiated accusations by persons whose qualifications to render any expert opinion on the matter are questionable at best, have caused many parents to resist having their children avail of life-saving vaccines that our government gives."

Doctors for Truth asked that the government not be too hasty in their dismissal of Dengvaxia, for as much of a risk as it presents for the naïve population, there is evidence that it is beneficial for the previously exposed:

"Given the recent findings of Sanofi Pasteur and recommendations of the WHO, we support the DOH decision to suspend its Dengvaxia immunization program until there is a quick and cost-effective way to determine whether a person has had dengue in the past or not. In the same light, given the findings that persistent, long term protection is given by the vaccine to those who have already gotten dengue infection, we urge the DOH not to remove the vaccine from the market altogether. Already we are faced with patients who have had dengue infection in the past, who are now at a loss because they cannot get their doses of Dengvaxia because it has been taken out of the market.

"We urge our colleagues in the medical profession to consider the greater good in all their statements and actions and to refrain from making premature conclusions based on insufficient data."

Looking for a way forward for the vaccine, David Loew, Head Global Commercial Operations Sanofi Pasteur, indicated there was a possibility of filing an application for the use of Dengvaxia in the United States. This decision is pending a meeting with the FDA.

There are several lessons learned from the Dengvaxia vaccine in the Philippines. First, it calls attention to the fact any vaccine being researched can have possible unknown side effects, and that these side effects may not be fully known until large numbers of people have been immunized. Second, it points to the importance of following well-established processes/procedures for the development and procurement of new vaccines. Lastly, it illustrates how vaccines can be perceived and ultimately trusted by the public.

We know vaccines can save lives. We also know getting them to those in need requires careful testing and deliberation. Dengvaxia, like any other vaccine, must undergo rigorous scrutiny to ensure its safety.

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