Chapter 2 Preparing International Travelers

Mark D. Gershman, Emily S. Jentes, Rhett J. Stoney (Yellow Fever) Kathrine R. Tan, Paul M. Arguin (Malaria)

The following pages present country-specific information on yellow fever (YF) vaccine require­ments and recommendations (Table 2-06) and malaria transmission information and prophy­laxis recommendations. Country-specific maps of malaria transmission areas, country-specific maps depicting yellow fever vaccine recommen­dations, and a reference map of China are included to aid in interpreting the information. The information was accurate at the time of publication; however, this information is subject to change at any time as a result of changes in disease transmission or, in the case of YF, changing country entry requirements. Updated information reflecting changes since publication can be found in the online version of this book (www.cdc.gov/yellowbook) and on the CDC Travelers’ Health website (www.cdc.gov/travel). General recommendations for other vaccines to consider during the pretravel consultation can be found on the CDC Travelers’ Health website (www.cdc.gov/travel).

YELLOW FEVER

Since publication of the 2018 edition of the CDC Yellow Book, large YF outbreaks occurred in eastern Brazil in 2017 and 2018, involving states where YF was not previously considered endemic. Notably, human YF cases occurred within the greater metropolitan area of São Paulo City and not far from the metropolitan limits of Rio de Janeiro City. In response, the Brazil Ministry of Health conducted mass vaccination campaigns in the newly affected areas. Based on a review of the situation by the World Health Organization (WHO) Scientific and Technical Advisory Group on Geographical Yellow Fever Risk Mapping, in which CDC par­ticipates, preliminary expanded YF vaccination recommendations were made for international travelers to the eastern and southeastern states of Brazil. Given that the Brazil Ministry of Health has initiated its plan to vaccinate the entire population of Brazil against YF by mid-2019, these preliminary vaccination recommendations for international travel will likely be made permanent by the advisory group.

Revaccination against yellow fever was previously required by certain countries at 10-year intervals to comply with International Health Regulations (IHR). In 2014, the World Health Assembly (of WHO) adopted the recommendation to amend the IHR by removing the 10-year booster dose requirement, and stipulated a 2-year transition period for this change. Consequently, as of July 11, 2016, a completed International Certificate of Vaccination or Prophylaxis (ICVP) is valid for the lifetime of the vaccinee. Moreover, countries cannot require proof of revaccination (booster) against yellow fever as a condition of entry, even if the last vaccination was >10 years prior.

In the United States, the Advisory Committee on Immunization Practices (ACIP) published a new recommendation in 2015 that 1 dose of yellow fever vaccine provides long-lasting protection and is adequate for most travelers. The recommendation also identifies specific groups of travelers who should receive additional doses and others for whom additional doses may be considered. For details, see Chapter 4, Yellow Fever. For the most up-to-date information about yellow fever vaccine boosters, consult the CDC Travelers’ Health website or the specific publication posted on the ACIP website (www.cdc.gov/mmwr/pdf/wk/mm6423.pdf).

Ultimately, the clinician’s decision whether or not to vaccinate any traveler must take into account the traveler’s risk of being infected with YF virus, country entry requirements, and individual risk factors for serious adverse events after YF vaccination (such as age and immune status). For a thorough discussion of YF and guidance for vaccination, see Chapter 4, Yellow Fever.

NOTE: Despite the recent changes to the IHR regarding YF vaccine boosters, it is uncertain whether all countries with YF vaccination entry requirements will fully adopt this change. Even if countries modify their official policies to extend the validity period of the ICVP from 10 years to the lifetime of the vaccinee, there is no guarantee that all national border officials will be aware of such policy change or be able to enforce it. CDC obtains information yearly from WHO about official country entry requirements. WHO likely will not be asking countries about YF vaccine booster entry requirements in the yearly questionnaires, because it will be assumed that countries are complying with the amended IHR. This could leave a gap in the foreseeable future in accurate published information about entry requirements for YF vaccine boosters for certain countries. Past experience has demonstrated that information given by consulates and embassies about vaccination requirements is often not accurate. Therefore, providers and travelers should not rely solely on such information when determining current YF vaccination entry requirements for specific destinations. With the caveats described above, readers should refer to the online version of this book (www.cdc.gov/yellowbook) and the CDC Travelers’ Health website (www.cdc.gov/travel) for any reported updates to country entry requirements since publication of this edition. 

MALARIA

The following recommendations to protect travelers from malaria were developed by using the best available data from multiple sources. Countries are not required to submit malaria surveillance data to CDC. On an ongoing basis, CDC actively solicits data from multiple sources, including WHO (main and regional offices); national malaria control programs; international organizations, such as the International Society of Travel Medicine; CDC overseas staff; US military; academic, research, and aid organizations; and published records from the medical literature. The reliability and accuracy of those data are also assessed. If the information is available, trends in malaria incidence and other data are considered in the context of malaria control activities within a given country or other mitigating factors such as natural disasters, wars, and other events that may affect the ability to control malaria or accurately count and report it. Factors such as the volume of travel to that country and the number of acquired cases reported in the US surveillance system are also examined. Based on all those considerations, recommendations are developed to try to accurately describe areas of the country where transmission occurs, substantial occurrences of antimalarial drug resistance, the proportions of species present, and the recommended prophylaxis options.

These recommendations should be used in conjunction with an individual risk assessment, taking into account not only the destination country but also the detailed itinerary including specific cities, types of accommodation, season, and style of travel, as well as special health conditions such as pregnancy.

Several medications are available for malaria prophylaxis. When deciding which drug to use, clinicians should consider the specific itinerary, length of trip, drug costs, previous adverse reactions to antimalarials, drug allergies, and medical history.

For a thorough discussion of malaria and guidance for prophylaxis, see Chapter 4, Malaria.

FOOTNOTES

Yellow Fever
¹ The official WHO list of countries with risk of YF virus transmission can be found in Table 4-23. Proof of yellow fever vaccination should be required only if traveling from a country on the WHO list, unless otherwise specified. The following countries, containing only areas with low potential for exposure to YF virus, are not on the WHO list: Eritrea, Rwanda, São Tomé and Príncipe, Somalia, Tanzania, Zambia.
² An elevation of 2,300 m is equivalent to 7,546 ft.

Malaria
³ Refers to P. falciparum malaria unless otherwise noted.
⁴Tafenoquine can cause potentially life-threatening hemolysis in people with G6PD deficiency. Rule out G6PD deficiency with a quantitative laboratory test before prescribing tafenoquine to patients.
⁵Mosquito avoidance includes applying topical mosquito repellant, sleeping under an insecticide treated mosquito net, and wearing protective clothing (e.g., long pants and socks, long sleeve shirt). For additional details on insect bite precautions, see Section 4, Mosquitoes, Ticks & Other Arthropods.
⁶Primaquine can cause potentially life-threatening hemolysis in people with G6PD deficiency. Rule out G6PD deficiency with a quantitative laboratory test before prescribing tafenoquine to patients.
⁷P. knowlesi is a malaria species with a simian host (macaque). Human cases have been reported from most countries in Southeast Asia and are associated with activities in forest or forest-fringe areas. This species of malaria has no known resistance to antimalarials.

Yellow Fever Maps
¹ This map is an updated version of the 2010 map crated by the Informal WHO Working Group on the Geographic Risk of Yellow Fever.
² Yellow fever (YF) vaccination is generally not recommended in areas where there is low potential for YF virus exposure. However, vaccination might be considered for a small subset of travelers to these areas who are at increased risk for exposure to YF virus because of prolonged travel, heavy exposure to mosquitoes, or inability to avoid mosquito bites. Consideration for vaccination of any traveler must take into account the traveler’s risk of being infected with YF virus, country entry requirements, and individual risk factors for serious vaccine-associated adverse events (such as age or immune status).