News Scan for Apr 19, 2018

Yellow fever risk
Rotavirus vaccine and intussusception

WHO identifies international cities most at risk for yellow fever

The World Health Organization (WHO) released a new assessment of international cities most at risk for yellow fever transmission, and Miami made the cut.

The study used flight data from 2016 to track cities that play host to both the Aedes aegypti mosquito (the vector that carries yellow fever) and visitors from yellow fever–endemic areas.

Researchers found that 45.2 million international air travelers departed from yellow fever–endemic areas of the world, and 11.7 million of those travelers went to 472 cities in which yellow fever was not endemic but had the potential for virus transmission. Almost two thirds of travelers (7.7 million or 65.7%) were not required to provide proof of yellow fever vaccination upon arrival.

Miami does not require proof of yellow fever vaccination status, and the WHO said such a requirement is up to each country's discretion. The vast majority of cities (89%) included in the study that have yellow fever endemicity do require proof of vaccination, including major cities in Brazil, India, and China.

"With more than 3 billion domestic and international passengers now boarding commercial flights each year, humans have become the primary agents for the global spread of mosquito-borne viruses such as dengue, chikungunya, Zika and yellow fever. Our findings on yellow fever virus transmission provide countries with insights into contemporary vulnerabilities to international spread of the virus," the authors wrote.
Apr 11 WHO


African rotavirus vaccine study reassures over bowel obstruction concerns

In a study based in Africa to explore postlicensing reports in middle- and high-income countries of an association between rotavirus vaccination and intussusception, a type of bowel obstruction, researchers yesterday reported that the risk is no higher than the background level. A team from African nations, the World Health Organization (WHO), and the US Centers for Disease Control and Prevention (CDC) reported its findings today in the New England Journal of Medicine.

In children younger than 5 years, rotavirus is responsible for about 37% of deaths from diarrhea each year, with the impact disproportionately high in sub-Saharan Africa. Associations between the vaccine and intussusception led to the withdrawal of an older version of the rotavirus vaccine, and the WHO has recommended careful monitoring during clinical trials of two newer vaccines, which found an increased risk, but not enough to outweigh the benefits of the vaccine.

For the new study, the researchers analyzed surveillance data from February 2012 through December 2016 from hospitals in seven sub-Saharan African countries that were among the first to start using the vaccine: Ethiopia, Ghana, Kenya, Malawi, Tanzania, Zambia, and Zimbabwe. They based their findings on 717 infants who had intussusception and confirmed rotavirus vaccination.

The risk of developing the condition 1 to 7 days after the first vaccine dose was not higher than the background risk, and findings were similar within a week of receiving the second dose. When they looked at the 21-day windows after both doses, they also found no higher risk than the background level.

In a press release today from the WHO Regional Office for Africa, Felicitas Zawaira, MD, who directs its family and reproductive health cluster, said the absence of the intussusception risk in African countries is reassuring, "particularly given the large public health benefits of rotavirus vaccination as demonstrated by ongoing rotavirus vaccine impact evaluation."

Matshidiso Moeti, MD, the office's regional director, said "These studies conducted in the African Region can serve as a model for other regions where wide-scale rotavirus vaccine introductions are just beginning and surveillance is ongoing as part of the WHO-coordinated Global Rotavirus Surveillance Network."
Apr 19 N Engl J Med study
Apr 18 WHO Regional Office for Africa press release

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