Following the release of new information about Dengvaxia® by Sanofi Pasteur about an increased risk of severe dengue infection several years after vaccination among people who had not been exposed to dengue prior to vaccination, and the Philippines Department of Health (DOH) decision to suspend vaccinations, Brazil’s National Sanitary Surveillance Agency (ANVISA) recommends that people who have never had contact with the virus do not take the vaccine.
Sanofi reported on a follow-up study comparing vaccinated people already infected with dengue with uninfected people. The groups were followed up for six years from the first dose.
Preliminary data showed that people not infected with dengue fever before receiving the vaccine may be more likely to develop more severe forms of the disease if they were bitten by a mosquito infected with dengue.
The recommendation of Anvisa is: people who are HIV negative (who have never had contact with the dengue virus) should not take the vaccine.
What is Anvisa’s recommendation for the dengue vaccine?
The recommendation is: people who have never had contact with the virus do not take the vaccine.
This is a precaution, since the preliminary data of this complementary study are not conclusive. In other words, it is not yet statistically confirmed whether there is an increased risk in the age group for which the vaccine is indicated (9 to 45 years).
For those who live in areas where dengue epidemics have never been recorded, the recommendation is not to take the vaccine because people in these areas are probably seronegative (never had contact with the dengue virus).
Residents of areas where a dengue epidemic has occurred should evaluate, together with their doctor, the recommendation of the vaccine to define the risks of the disease and the potential benefits and risks of vaccination.
Why have these studies only arisen now?
Every new drug continues to be monitored and researched upon receipt of registration upon reaching the market. This phase is called post-market and serves exactly to identify situations not described during the clinical research phase, only identifiable with the large-scale use and its long-term follow-up. Data from the six-year follow-up studies were sent by the manufacturer as soon as they were ready.
In the case of the dengue vaccine, the pre-registration research phase brought together about 40,000 people from different parts of the world, including Brazil. However, even with this amount of people some cases appear only when the drug starts to be used by a larger group of people.
“Having contact with the virus” is the same as getting sick?
No. Most people already infected with dengue viruses do not know that. That is, there are people infected by the virus, but they do not develop the symptoms of the disease.
What is the risk to who took the vaccine?
First, it is important to clarify: the vaccine does not cause dengue. Who causes dengue is the virus, present in most of Brazil. People vaccinated or not, when bitten by infected mosquitoes, may or may not have symptoms of the disease.
The study found that whoever took the vaccine and never had prior contact with the virus may present a 0.5% higher risk of hospitalization and 0.2% for severe dengue compared to previously vaccinated persons.
I took the first dose of the vaccine, should I take the other doses?
There is no data on the risk of severe illness and hospitalization according to the number of doses received.
Persons already vaccinated, with one or two doses, should seek care from a health professional to assess the characteristics of the disease in the region where the patient lives, intensity of transmission and age to evaluate the benefit of completing or not the vaccination schedule.
But if I ever had dengue because I would take the vaccine?
Dengue is a disease caused by four different serotypes, it is as if they were four types of dengue. So even if you have ever had dengue, you may fall ill again for another serotype. In addition, the vaccine is not 100% effective against the virus, as is already stated in the package leaflet.
I do not think I’ve ever had dengue, what do I do?
If you live in areas where dengue epidemics have never been recorded, the recommendation is not to take the vaccine because people in these areas are probably seronegative (never had contact with the dengue virus).
If you live in areas where a dengue epidemic has already occurred, it is important to evaluate, together with your doctor, the recommendation of the vaccine to discuss the risks of the disease and the potential benefits and risks of vaccination.
I have already vaccinated, now what?
The guideline is the same for people vaccinated or not, ie all must maintain should maintain preventive measures against mosquito bite after vaccination and should seek a doctor if they develop signs of dengue. These signs are persistent high fever for more than two days, pain or tenderness abdominal pain or tenderness, persistence of vomiting, mucosal bleeding, drowsiness and hyperactivity, according to WHO guidelines, 2009.
What kind of gravity are we talking about?
In the scale of 1 to 4 (being 4 the highest, according to WHO classification of 1997), used in the study the majority of the cases were in 1 and 2, that is to say, less serious. No deaths were recorded during clinical studies related to vaccination and all cases recovered with routine treatment.
Why do people already vaccinated have dengue?
No vaccine guarantees 100% protection. In the case of the dengue vaccine the average is 66% protection, reduction of hospitalizations of 80% and protection against severe forms of 93% after the third dose of the vaccine.
- Venezuela measles (sarampión) update: More than 400 cases in Bolívar state
- Missouri reports a significant increase in flu early on
- Quincy: Legionnaires’ disease case reported in Veteran’s Home resident
- Strongyloides stercoralis hyperinfection: Researchers identify chemical that suppresses parasite
- Crown Princess outbreak update: Clostridium perfringens food poisoning implicated
- Walter Reed-developed Zika vaccine induces strong immune response in three phase 1 studies