Yellow Fever Vaccination Does Not Increase Severe Dengue Risks

Don Ward Hackett

Yellow Fever Vaccination Does Not Increase Severe Dengue Risks

Dengue vaccine Dengvaxia is a live, attenuated vaccine now approved by the US FDA

May 8th, 2019 – A new, long-term study found no evidence that a Yellow Fever virus vaccination in dengue-endemic areas increased the risk of Severe Dengue Fever.   

This is good news since serological interactions between the dengue virus and other flaviviruses, such as Yellow Fever, could drive antibody-dependent enhancements, which is associated with disease severity in dengue infections. 

Severe Dengue affects most Asian and Latin American countries and has become a leading cause of hospitalization and death among children and adults in these regions, says the World Health Organization (WHO). 

Additionally, both dengue and Yellow Fever virus outbreaks have been reported in similar countries during 2019. 

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This study evaluated the severity of 11,448 lab-confirmed dengue cases reported in São José do Rio Preto, Brazil.

7,370 patients had been vaccinated for Yellow Fever and they were compared to 4,078 unvaccinated patients. 

These researchers regressed dengue severity against Yellow Fever (YF) vaccine status and a number of demographic, clinical, and laboratory variables as controls between 1998 and 2006. 

And, they also evaluated the association between YF vaccination status and the clinical and laboratory symptoms of dengue patients. 

The study did not find any evidence of increased risk for severe dengue in patients vaccinated against YF (odds ratio = 1.00; 95% confidence interval = 0.87–1.14).

According to the WHO, from July 2018 through March 2019, Brazil recorded a Yellow Fever case-fatality ratio of 23 percent. 

In the USA, there are 2 FDA Yellow Fever vaccines available during 2019, YF-Vaxand Stamaril. 

Recently, the US Food and Drug Administration (FDA) approved the dengue vaccine Dengvaxia for use in the USA for individuals 9 through 16 years of age.

Dengvaxia has already been approved in 19 countries and the European Union. 

Sanofi Pasteur’s Dengvaxia is a live, attenuated vaccine that is administered as 3 separate injections, with the initial dose followed by two additional shots given 6 and 12 months later. 

Dengvaxia was determined to be approximately 76 percent effective in preventing symptomatic, laboratory-confirmed dengue disease in individuals 9 through 16 years of age who previously had laboratory-confirmed dengue disease. 

Dengvaxia is not approved for use in individuals not previously infected by any of the dengue virus 4 serotypes or for whom their immunization information is unknown. 

This study was published in Travel Medicine and Infectious Disease on May 8, 2019.

No conflicts of interest were disclosed by these researchers.

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Traveling abroad this summer - here are some tips from CDC?

Summer Travel Abroad

Escaping to an overseas retreat this summer? It’s the time of year when people start planning their summer vacation. If you venture abroad for some summer fun, there are health and safety risks you should be aware of. No matter where you go—majestic mountains, secluded beaches, or bustling cities—kick off your travel adventure by getting prepared with our summer vacation tips.

Before You Trip

• Check your destination for health concerns. Even if you’re familiar with the place, there may be new and important health risks you should be aware of.
• Make an appointment with a travel medicine specialist or your healthcare provider to get important advice, vaccines, and medicine at least one monthbefore you leave.
  • CDC recommends all travelers be up to date on routine vaccines, including measles, mumps, and rubella (MMR), varicella (chickenpox), and your seasonal flu vaccine, which you should be able to get from your doctor.
• Pack a travel health kit with your prescription and over-the-counter medicines (enough to last your whole trip, plus a little extra), first aid supplies, your health insurance card, and more.
• Prepare for the unexpected.

• Enroll in the State Department’s Smart Traveler Enrollment Program (STEP) to get the latest safety updates and help in an emergency.
• Leave copies of your itinerary, contact information, credit cards, and passport with someone at home, in case you lose them during travel.
• Find out if your health insurance covers medical care abroad—many plans don’t!
• Consider buying additional insurance that covers health care and emergency evacuation, especially if you will be traveling to remote areas.

Health Risks and Outbreaks

Zika, Dengue, and Malaria Risks

• Zika. Many popular summer travel destinations still have a risk of Zika. Check CDC’s Zika Travel Information to find out if there is a risk of Zika at your destination and how to protect yourself during and after travel. Zika can cause serious birth defects if a woman is infected during pregnancy. Pregnant women shouldnot travel to an area with a Zika outbreak. Pregnant women considering traveling to other areas with Zika risk should discuss travel plans with their doctor, the risks and consequences of possible Zika infection, and their willingness to accept that risk if they choose to travel.
• Dengue viruses are spread to people primarily through the bite of an infected mosquito. Symptoms of mild dengue include fever with any of the following: nausea, vomiting, rash, aches and pains (eye pain typically behind the eyes, muscle, joint, or bone pain). Mild dengue symptoms can become severe within a few hours. Severe dengue is a medical emergency. There is no vaccine to prevent dengue, and there is no treatment. Protect yourself by preventing mosquito bites.
• Malaria is a parasitic disease spread by mosquitoes. It can lead to serious illness and can be fatal if left untreated. Symptoms of malaria can include fever, chills, nausea, vomiting, and body aches. If symptoms of malaria occur, travelers should seek medical attention immediately. Before you leave home, check your destination for a risk of malaria. If malaria is present, consult your doctor to assess your risk and choose the most appropriate anti-malarial medicine. Pregnant women infected with malaria can transmit the parasites to their child during pregnancy or delivery. CDC recommends that pregnant women talk to their doctor if traveling to areas with risk of malaria. When used as directed, EPA-registered insect repellents are safe for pregnant and breastfeeding women.

Measles Outbreaks

Where? There are measles outbreaks in many popular destinations.

What are the consequences? Measles is highly contagious and can cause serious long-term health complications.

What should you do? Before you travel, talk to your doctor to make sure you and your traveling companions are up to date on the MMR (measles, mumps, and rubella) vaccine. Don’t put yourself and others at risk!

During Your Trip

• Always wear seat belts and choose safe transportation. Motor vehicle crashes are the #1 killer of healthy US citizens in foreign countries.
  • Ride only in marked taxis or ride-sharing vehicles.
  • While walking, be alert when crossing the street, especially in countries where people drive on the left.
  • Avoid overcrowded, overweight, or top-heavy buses or vans.
• Eat and drink safely. Contaminated food or drinks can cause travelers’ diarrhea, the most common travel-related illness, and other diseases. If you are traveling to a developing country, you are especially at risk.
  • When possible, choose food that is cooked and served hot, washed in safe water, or peeled.
  • Stick to drinks that are bottled and sealed, or very hot coffee or tea, and avoid ice.
• Protect yourself from hot temperatures and sun exposure.
  • Wear SPF 15 or higher sunscreen to protect yourself from the sun’s harmful UV rays when enjoying outdoor activities.
  • Follow the instructions on the label and reapply as directed.
• Prevent insect bites. Using insect repellent can protect you from serious diseases spread by mosquitoes, such as Zika, dengue, yellow fever, and malaria.
  • Use an EPA-registered insect repellent with one of the following active ingredients: DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone.
  • Apply sunscreen first, then repellent.
  • Follow the instructions on the label and reapply as directed.
  • If you’re sleeping in a room without screens or air conditioning, or a tent- sleep underneath a mosquito net and make sure it’s tucked into your mattress.
• Avoid Animals. We know that this advice is no fun- but any animal, even if it appears to be friendly or harmless, can be dangerous.
  • Never try to pet, handle or feed unfamiliar animals, even pets, as they may not be vaccinated against rabies.
  • If you are bitten or scratched, immediately wash the wound with plenty of soap and water and see a doctor as soon as possible!

After Your Trip

Some travel-related illnesses may not cause symptoms until after you get home. If you get sick after your trip, call your doctor and be sure to tell them about your travel, including where you went and what you did on your trip. This will help your doctor consider infections that are rarely found in the United States.

• If you need help finding a travel medicine specialist, find a clinic here.
• For more information, see Getting Sick after Travel.