Yellow Fever Outbreaks: Are There Enough Vaccines to Stop Them?

Increasing outbreaks are depleting the world's stores

Yellow fever has been spreading in Angola in 2016, with over 1000 people infected and over 250 dead. The virus, spread by mosquitoes, has spread throughout the country but primarily has been in and around the capital.

Interestingly, the situation sounds like something out of a science fiction story: The world is running low on its stockpiles of the vaccine for the virus. Those carrying the virus have traveled thousands of miles away, taking the virus to where it's never been seen before, and although everyone in a yellow fever area should be vaccinated against it, many are not.

Many foreign workers in Angola were not vaccinated. Some returned home carrying the virus and became sick. China for the first time reported a case of yellow fever. Fortunately, although China has the mosquito which spreads the virus, yellow fever didn't arrive in the season or location when and where the mosquito was common. Besides a few cases in China, the virus has also been found across the border in the DRC and imported to Kenya. There are also unrelated outbreaks in Uganda and the DRC, as well as cases reported in Peru.

What Can Be Done to Stop This?

There is a vaccine. The problem is, there's not enough of it and it can't always be distributed quickly enough.

Is the Vaccine Good?

It's a very effective vaccine. The World Health Organization (WHO) describes the vaccine as safe and effective and able to provide immunity in one week to 95 percent of those who are vaccinated. In 30 days, 99 percent have developed passive immunity.

Taken 10 days before travel, the vaccine should be effective in preventing yellow fever. The virus is easy to prevent, but nothing treats it. 

Why Aren't There Enough Vaccines?

The Angola outbreak has already depleted the global vaccine stockpile. There had been six million vaccines available, but there are 21.5 million people in Angola and 67.5 million in neighboring DRC.

Even if most people were already vaccinated, that are a lot of vaccines still needed.

Production of the vaccine is slow and requires eggs for manufacture. Only four facilities in the world make the vaccine. The facility in Dakar, Senegal makes 10 million a year.

What is being done?

The WHO has recommended providing 1/5th the normal dose, if doses are running low. This means 5 people could be treated with as much vaccine as normally given. Those in affected areas may be given lower doses, though some campaigns are continuing to give full doses.

The documentation for these lower dose vaccines will be different. Those vaccinated with lower doses will be asked to return for repeat vaccination within a year in order to be better protected longterm. Normally the vaccine can protect for many years - even potentially a lifetime.

Am I Safe If I Last Received the Vaccine Over 10 Years Ago?

You may not need to get another vaccine. The vaccine officially lasts 10 years. It used to be that a booster was routinely recommended after 10 years.

It is now not routinely recommended, though the CDC says "travelers to Angola may consider getting a booster if their last yellow fever vaccine was more than 10 years ago." The WHO, however, states that a booster is not needed.

The CDC Advisory Committee on Immunization Practices (ACIP) recommended in 2015 that one dose provided enough "long-lasting protection," that it was sufficient for most travelers. However, some may need an extra vaccine anyways. These include:

  • those required to do so by the country they are visiting
  • those who were pregnant when first vaccinated
  • those who have HIV or who have now had a stem cell transplant since their last vaccination
  • some laboratory workers handling yellow fever virus samples
  • those who will have a higher risk based on duration of trip, location and timing of trip, and specific exposures.

Who Is Most Likely to Get Sick? 

Of those exposed to yellow fever without being vaccinated, those most likely to get sick are the young and the old. Once you get yellow fever, you shouldn't be at risk a second time, but that's not the way you want to protect against the infection.

There are likely genes that make some of us more likely to catch and become sick from yellow fever. It's thought that like with the related West Nile Virus, the CCR5 gene may play a role. When people lack a functional CCR5 gene, they are much less likely to catch HIV, but they are at increased risk of becoming very sick with West Nile.

It might possibly be that those lacking a functional CCR5 gene are more likely to get sick with yellow fever (or very, very rarely from vaccination for it). Less than 1 percent of the population lacks the CCR5 gene (mostly those with European ancestry; about 1 percent of white Europeans and Americans).

How Can I Protect Against Mosquitoes?

Those who have yellow fever should, as the CDC recommends, stay indoors, under a mosquito net if possible for 5 days or so after the fever starts, so as to avoid spreading the virus to others. It's important to get rid of standing water, where mosquitoes breed around the home, and to use long sleeves to cover up. You should close windows and maybe use air conditioning, if possible. You should also use insect repellent to avoid mosquito bites.

Where Is the Vaccine Needed?

Because the virus is not found throughout all of these countries, but sometimes only in particular areas, the vaccine may not be required for all travel. There are 44 countries at risk.

Some countries at risk for yellow fever require vaccination for all travelers. This list can vary, so please check embassy, consulate, or state department information before traveling. Recently, the list of countries requiring yellow fever vaccination included Angola, Benin, Burkina Faso
Burundi, Cameroon, Central African Republic, The Republic of Congo, Côte d’Ivoire, Democratic Republic of Congo, French Guiana, Gabon, Guinea-Bissau, Liberia, Mali, Niger, Rwanda, Sierra Leone, and Togo. Except for French Guiana, all of these countries are in Africa.

Other countries require yellow fever vaccination if you've traveled to a country at risk. There is concern that the virus could be imported, so if you've traveled to a country at risk for yellow fever and didn't get vaccinated, you may still need the vaccine to be able to travel to other countries.

For instance, many countries which do not currently face yellow fever have the environment and the mosquitoes needed to spread the disease. Some of these countries require vaccination if arriving from an affected country, even if just for a layover for 12 hours. The list of countries is subject to change, but does include, for instance, countries like Mozambique, South Africa, Tanzania, Trinidad and Tobago, Uganda, Vietnam, Yemen, Zimbabwe, Zambia, and other countries. Check vaccination requirements before traveling to be sure.

How Is Vaccination Documented?

Documentation of yellow fever vaccination is through an official Yellow Card. This is actually literally a yellow card that is carried with a passport to show that the person is safe to travel.

The vaccine needs to be taken 10 days before travel. It may be difficult to find the vaccine and so planning ahead of time is helpful.

There is a problem with falsifications of yellow fever card. It's important to actually be vaccinated and not just get a card that says you have been.

Who Shouldn't Get the Yellow Fever Vaccine?

The vaccine is for those over 9 months of age. Infants under 6 months shouldn't be vaccinated. The vaccine is produced with eggs, so don't get vaccinated if you have a severe allergy to eggs, chicken proteins, gelatin, or the yellow fever vaccine itself.

There are others who may have problems with the vaccine. Talk to your doctor about the vaccine if you

  • have a weakened immune system, such as from HIV, cancer, an organ transplant, immunosuppressive drugs, or another immunodeficiency, such as one you were born with
  • have certain thymus disorders

There are other times when you should talk to your doctor about weighing the risks and benefits of the vaccine. It may be that you should get vaccinated or that you should avoid travel to affected areas. Those who should talk to their doctor include those who are:

  • Over 60 years of age
  • Between 6-8 months
  • Pregnant or nursing
  • HIV positive but do not have any symptoms or any problems with their immune system
  • Have thymus disorders

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