On 21 February 2020, the World Health Organization (WHO) classified Uganda as a high-risk country in the “Eliminate Yellow Fever Epidemics” (EYE) initiative, with a history of recent outbreaks in 2019, 2018, 2016 and 2011.
Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes and has the potential to spread rapidly and cause serious public health impact.
According to the WHO, Uganda’s classification is a risk as the estimated overall population immunity is low (4.2%), and attributable to past reactive vaccination activities in focal districts that are not affected by the current outbreak.
Before classifying Uganda as high-risk, Uganda had eight laboratory confirmed cases of yellow fever in Buliisa (3), Maracha (1) and Moyo (4); including four deaths (CFR 50%), were detected through the national surveillance system.
Public health response
National rapid response teams were deployed to Moyo and Buliisa districts to conduct further investigations, and initiate outbreak response. Other response activities include: enhanced surveillance and active case finding in all districts in the north-west region, and entomological surveys in the affected districts of Buliisa and Moyo. Cross-border notification with South Sudan in reference to the cases in Moyo district has been done. Investigations went on in DRC and South Sudan.
The Ministry of Health then staged a reactive campaign, approved by the International Coordinating Group on Vaccine Provision for Yellow Fever Control. This reactive campaign targeted approximately 1.7 million people to stop transmission and prevent imminent risk of the outbreak spreading in the north-west part of the country particularly in Buliisa, Koboko, Maracha, Moyo and Yumbe districts. To achieve sustained protection across the country, the MoH prepared to apply for the introduction of yellow fever vaccination into the routine immunization programme in 2021 and implementation of preventive mass vaccination campaigns nationally.
But the WHO assessment revealed that the infections were due to the negligible population immunity in the affected districts and that the detection of yellow fever cases were concerning. “The affected districts share international borders with both DRC and South Sudan; and are marked by frequent population movements and high interconnectivity. Population immunity for yellow fever in the cross-border areas is also low and the forest biome between countries is continuous, indicating that there is a risk of international spread. Close monitoring of the situation with active cross-border coordination and information sharing is needed as the possibility of cases in neighbouring countries and risk of onward spreading to DRC and South Sudan cannot be completely excluded,” part of the statement reads.
WHO advice
The WHO says that vaccination is the primary means for prevention and control of yellow fever and provides immunity for life. In urban centres, the WHO adds, targeted vector control measures are also helpful to interrupt transmission. Uganda planned to introduce yellow fever vaccination into the routine immunization program and complete preventive mass vaccination activities to rapidly boost population immunity. Expedited planning and implementation of these activities to protect the population will help avert risk of future outbreaks.
According to the statement, the WHO recommends vaccination against yellow fever for all international travelers aged 9 months and above entering Uganda as there is evidence of persistent or periodic yellow fever virus transmission.
“Yellow fever vaccination is safe, highly effective and provides life-long protection. However, yellow fever vaccination is not recommended for infants aged 6 to 8 months, except during epidemics when the risk of yellow fever virus transmission may be very high. The risks and benefits of vaccination in this age group should be carefully considered before vaccination. The vaccine should be used with caution during pregnancy or breastfeeding,” reads the statement.
However, the WHO warned: “pregnant or breastfeeding women may be vaccinated during epidemics or if travel to a country or area with risk of transmission is unavoidable. Uganda also requires, as a condition of entry, a valid yellow fever vaccination certificate for travellers aged 1 year and above.”
In accordance with the International Health Regulations (2005) Third Edition, the international certificate of vaccination against yellow fever is valid from 10 days after vaccination and throughout the life of the person vaccinated.
“A single dose of WHO approved yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against yellow fever disease. A booster dose of the vaccine is not needed and is not required of international travelers as a condition of entry,” the WHO says.
“WHO encourages its Member States to take all actions necessary to keep travelers well informed of risks and preventive measures including vaccination. As a general precaution, WHO also recommends avoidance of mosquito bites. The highest risk for transmission of yellow fever virus is during the day and early evening. Travelers should be made aware of the signs and symptoms of yellow fever and instructed to rapidly seek medical advice if experiencing signs and symptoms suggestive of yellow fever infection. Viraemic returning travelers may pose a risk for the establishment of local cycles of yellow fever transmission in areas where a competent vector is present,” the WHO says.
However, WHO does not recommend any restrictions on travel and trade to Uganda on the basis of the information available on the outbreak.
Public announcement
Meanwhile, the National Medical Stores is conducting a free Mass yellow fever vaccination exercise at Mayor’s Garden, Entebbe. The campaign started on Thursday 19th and will end on Monday 30th August.
“Come get vaccinated against Yellow Fever at no cost!” part of the MoH message to the public reads.
The MoH, however, clarified that: “Please note that the following categories of people are not supposed to be vaccinated against yellow fever: Pregnant women, Children below 9 months, and anyone above the age of 60.”