The United States is facing a shortage of yellow fever vaccine that could stretch into next year, the Centers for Disease Control and Prevention warned Friday.
While measures are being taken to alleviate the impact, travelers who need to be vaccinated against the virus may have a hard time getting the injection and may have to travel within the US to do so. Where 4,000 clinics normally offer yellow fever vaccinations, merely 252 in the country will have vaccine while the shortage persists.
The tight supplies could cause significant disruption for some travelers. Eighteen countries — most in sub-Saharan Africa, but also French Guiana in South America — require that incoming travelers provide proof of yellow fever vaccination. Another 25 countries in Central and South America and in Africa are deemed to be places where a risk of yellow fever transmission exists and vaccination may be recommended. Still other countries require travelers coming from a place where yellow fever spreads to prove they have been vaccinated.
And the CDC is not suggesting people forgo vaccination if they need it; yellow fever is a dangerous disease with a significant mortality rate. The yellow fever virus, like the related dengue and Zika viruses, is spread by mosquitoes. But it is more likely to kill than its cousins.
People who contract yellow fever can experience fever, headache, backache, muscle pains, loss of appetite, and nausea or vomiting. Those symptoms generally resolve after a few days. But about 15 percent of people then suffer a relapse, entering a second phase of the illness during which they develop jaundice and more severe illness. Roughly half of the people who reach this so-called toxic phase die.
Only four manufacturers in the world make yellow fever vaccine, and only one product — made by Sanofi Pasteur — is licensed in the US.
Global supplies have been tight for the past year or so, a problem that began when Angola experienced an unprecedentedly large outbreak of urban yellow fever last year that spread to the Democratic Republic of Congo. Bringing those outbreaks under control and extinguishing an unrelated epidemic in Uganda required 30 million vaccine doses.
Before the stretched-to-the-limit production cycle could recover, a large and alarming outbreak in Brazil — which is still ongoing — put new pressure on global supplies.
The challenge for the US supply relates to problems faced by the only manufacturer that sells yellow fever vaccine in this market, Sanofi Pasteur. The company, which makes the vaccine in Swiftwater, Penn., was in the process of shifting the production to a newer facility that would open in 2018.
But an unexpected manufacturing problem resulted in the loss of a large number of doses that would have been used to cover need during the transition period.
Sanofi sought and received permission from the Food and Drug Administration to bring a yellow fever vaccine it makes in France — the product, called Stamaril, is not licensed here — into the US to fill the gap. It will be used during this period under an emergency investigational new drug authorization.
The CDC said it looked at the possibility of recommending people be given a fractional dose of vaccine — one-fifth the normal dose — as a stopgap measure, but concluded there was too little data to show that approach works to endorse it.
Because of limited supplies last year, the World Health Organization urged the fractional dose approach be used in controlling the outbreak in the Democratic Republic of Congo. And Brazil has been considering it as its outbreak spreads and vaccine supplies tighten.