"Anyone 9 months or older who travels to or lives in these areas should be vaccinated against yellow fever," the CDC alert said.
‘Health officials say travellers should plan to get the vaccination before arriving in Brazil as the country is facing a shortage of the vaccine.’
Two of the largest mass vaccination campaigns against yellow fever ever seen in the world have begun in Nigeria and Brazil. Both campaigns, which are supported by the World Health Organization, aim to prevent the spread of the disease.
Yellow fever spreads to humans through the bite of an infected mosquito, and outbreaks usually occur in tropical regions, mainly in South America and Africa. Hundreds of monkeys died in the Atlantic rain forest in the states of Rio de Janeiro, Espirito Santo and Sao Paulo last year indicating that the fever was back in Brazil. Symptoms of yellow fever usually begin three to six days after a bite and last about three or four days. They are similar to the flu and could become severe to include fever, headache, muscle pain, nausea, vomiting, fatigue and jaundice — hence its name yellow fever.
According to WHO the mass immunization campaign launched in Brazil has begun delivering fractional doses of yellow fever to nearly 24 million people in Rio de Janeiro and Sao Paulo. When there is a short supply of vaccines, fractional dosing (a short term effective strategy) can extend vaccine supplies to more people who can be protected from the spread of the disease.
A full dose of vaccine can provide life-long protection against yellow fever. One-fifth of the regular full dose can provide immunity against the disease for at least 12 months, maybe even longer.
WHO spokesman Tarik Jasarevic says the goal of the campaign is to reduce yellow fever transmission by achieving 90 percent coverage in those states.
"It is a part of an initiative to eliminate yellow fever epidemics," he said. "As you know, we cannot ... eradicate the yellow fever virus because it is being transmitted by mosquitoes. But, with the effective vaccine that exists for a number of years now, it can be prevented. So, mass vaccination is the best way to prevent outbreaks of yellow fever."