By DONALD G. McNEIL Jr.
Published: May 17, 2013
One yellow fever shot confers lifetime protection and the customary “booster shot” given at 10 years is no longer necessary, the World Health Organization announced Friday. Yellow fever vaccine is relatively safe but causes more dangerous side effects than many other vaccines and is therefore normally given only to healthy people who are at risk. The mosquito-borne disease, for which there is no cure, strikes about 200,000 people worldwide each year and kills about 30,000 of them. Cases are increasing as deforestation increases contact with forest mosquitoes and the monkeys that harbor the virus. Only nine cases have been found in the United States over the past 30 years, all in travelers returning from Africa or Latin America, but eight were fatal, according to the Centers for Disease Control and Prevention. Dr. Thomas P. Monath, a yellow fever expert at the Harvard School of Public Health, said that the W.H.O. announcement made sense for almost all vaccine recipients, but that booster shots might still be needed for laboratory technicians working with the virus and for a few travelers who had one shot many years ago but whose immunity had waned.
A World Health Organisation advisory panel has confirmed that the protective effects of yellow fever vaccine are life-long, and that ten-yearly boosters are no longer needed to maintain immunity.
This news comes just in time for the 66th World Health Assembly – the annual meeting of the WHO’s decision body taking place this week in Geneva; but even if the findings are fully embraced, travel health requirements will take at least two to three years to be updated.
WHO regulations currently stipulate that yellow fever vaccination certificates are valid only for ten years, and every country will have to agree to any change.
Yellow fever is the only remaining disease for which a formal international vaccination certificate requirement still exists; previously, when cholera vaccination certificates were abolished by the WHO in 1973, it took 17 years for all countries to change their entry requirements, while border officials at some remote outposts continued to hassle incoming travellers for even longer.
Yellow fever is a dangerous virus infection transmitted by mosquitoes, occurring most often in parts of Africa – there is currently a serious outbreak in Sudan – and central and South America. Mosquito species capable of spreading the disease are found in many parts of the world that are currently free of infection, including many parts of Asia, which is why so many countries require travellers coming from risk areas to be vaccinated, in order to keep out the disease.
In recent years, yellow fever vaccination has become a more complicated issue: official risk maps have been changed, a rise in the rate of vaccine side effects above the age of 60 has been recognised, and countries (notably South Africa) have toughened up entry requirements for passengers arriving from risk areas.
The prospect of reducing the need for yellow fever vaccination to a single lifetime dose – with just one vaccination certificate that border officials will ever need to see – will simplify vaccine decisions, and make tropical travel much easier, but this change will take some time to trickle through.
By DONALD G. McNEIL Jr.