excerpt from The Vaccine Guide
Simple formula for vaccine decisions prior to international travel.
First, gather information about current disease incidence in the city, province, or specific area of a country on your itinerary.
Second, decide if the risks from vaccines for this disease outweigh your risk of exposure and significant illness.
Third, determine whether the vaccine’s efficacy is high enough to warrant risking its side effects.
Your decision is made.
Vaccines prior to travel fall into three general categories:
1. routine vaccines normally given in childhood that may have lapsed or you never received
2. exotic vaccines recommended for travel to specific countries
3. required vaccines for entry into specific countries (Yellow fever is the only vaccine currently in this category.)
Information about international disease incidence and recommended vaccines for travel can be obtained at the following websites:
www.cdc.gov This is the official website of the CDC that contains an extensive section for travelers’ health. Information includes disease incidence by region, recommended vaccines, and extensive information about the vaccines.
www.tripprep.com A private company, Shoreland, Inc., maintains this site of health conditions and recommendations, country by country.
For questions about disease incidence in specific areas you are visiting, call the CDC Traveler’s Health Hotline: 404 332-4559.
No vaccine is currently available in the US for cholera because of the limited duration of effectiveness produced by the vaccine.
Hepatitis A exists in many areas of the world where sanitation standards are relatively low. Transmission occurs through water contaminated with sewage. Travelers to North America (except Mexico), Japan, Australia, New Zealand, and developed countries in Europe are at no greater risk of infection than in the United States. But travelers to developing countries including the continents of South America, Africa, and Asia are at risk of contracting hepatitis A from contaminated water sources and raw foods. Traveling to rural areas and eating in settings with poor sanitation will increase the risk of contracting hepatitis A.
Three strategies exist for the prevention of hepatitis A.
First, avoid exposure. Do not drink the water, except safe, bottled water or boiled water. This includes brushing your teeth and ice in drinks. Peel all fruit, and do not eat salads or other raw foods. Do not buy food from street vendors. Do not swim in potentially polluted bodies of water.
Second, consider prevention with immune globulin (IG). This shot will provide protection against hepatitis A for up to 4-6 months. IG carries significantly less risk than the vaccine, and is probably more effective, though the duration of protection is limited. Protection also begins immediately following the injection. IG will provide more types of antibodies than those stimulated by the vaccines. IG can be used in infants. The vaccine, by contrast, cannot be used in anyone less than two years old.
Third, consider the hepatitis A vaccine. A single injection of vaccine will result in protective antibody titers after four weeks that persist for six months to one year. It is estimated that 95 to 100 percent of young, healthy adults develop protective levels of antibodies one month after vaccination. A booster dose 6-12 months later will produce protection that persists for up to ten years. In older adults the vaccine is less effective. In one study, only 70 percent of vaccine recipients aged 40 to 65 years developed adequate antibody responses compared to 91 percent of recipients 18 to 39 years old after a single dose of vaccine (Reuman et al., 1997). If travel is scheduled less than four weeks following vaccination, protection may not be adequate to prevent infection. No studies have been published that evaluate protection in travelers vaccinated less than two weeks prior to travel.
Serious adverse event reports for hepatitis A vaccine include anaphylaxis, Guillain-Barré syndrome, brachial plexus neuropathy, transverse myelitis, multiple sclerosis, encephalopathy, and erythema multiforme.
Hepatitis A Facts
·Avoidance of contaminated water and food is the best preventive.
·One dose of Immune Globulin will prevent hepatitis A with minimal side effects.
·Hepatitis A vaccine is associated with significant serious adverse effects.
Typhoid fever is caused by the bacterium Salmonella typhi, which is contracted from water contaminated with sewage. It is passed through the fecal-oral route. The same precautions should be observed as those for hepatitis A. In the United States, about 400 cases occur each year, and 70 percent of these are contracted while traveling internationally. Typhoid is most commonly acquired during travel to Asia, Africa, and Latin America.
The disease causes a sustained fever of 103° or higher accompanied by weakness, stomach pains, headache, or loss of appetite. Antibiotics can successfully treat typhoid, and deaths are extremely rare.
Oral live typhoid vaccine is taken as a capsule or liquid suspension in four doses. The most common side effects are abdominal pain, diarrhea, and vomiting. Serious adverse reactions have not been recorded, even in large population based trials. However, studies of vaccine efficacy have not fared so well. Studies have shown an average efficacy of about 70 percent (Lin et al., 2001). The oral vaccine is licensed only for adults and children over six years of age since the vaccine is ineffective in young children. In controlled field trials conducted among schoolchildren in Chile, three doses of the oral vaccine reduced infection by 66 percent over a period of 5 years (Levine et al., 1987; Levine et al., 1989), but in a subsequent trial vaccine efficacy was only 33 percent (Levine et al., 1990).
An inactivated polysaccharide vaccine given by injection has a similarly low effectiveness, averaging 60 to 70 percent (Jong, 1999). In a trial in Nepal among persons 5-44 years of age, vaccine recipients had 74 percent fewer cases of typhoid than occurred with controls (Acharya et al., 1987). In a trial involving schoolchildren in South Africa who were 5-15 years of age, one dose of the inactivated vaccine resulted in 55 percent fewer cases of typhoid fever over a period of three years than occurred with controls. (Klugman et al., 1987).
Killed, whole-cell vaccines given by injection are more effective, but have an unacceptably high rate of serious adverse reactions including shock, multiple sclerosis, autoimmune reactions, and kidney disease. Newer vaccines are also being investigated.
Typhoid Fever Facts
·Avoidance of contaminated water and food is the best preventive.
·Oral typhoid vaccine in a four-dose schedule and inactivated vaccine in a single injection are only 60-70 percent effective in preventing disease.
Yellow fever occurs in tropical areas of Africa and South America. It is a viral disease transmitted between humans, or from monkeys to humans, by mosquitoes in those areas of the world. Most cases occur in forestry and agricultural workers exposed in jungle locations, but sporadic epidemics occur, sometimes involving more than 30 percent of the population (Monath, 1999). Yellow fever is very rare in travelers.
The disease is characterized by three stages. The first includes a fever and flu-like stage with vomiting, nosebleeds, and a rash. This is followed by a period of calm, and then the onset of agitation, prostration, jaundice, bleeding from multiple sites, kidney failure, and death. In an epidemic during 1969 in Nigeria, 45 percent of hospitalized patients died (Jones et al., 1972). Overall case fatality rates in epidemics are about 20 percent (Wilson, 2001). Modern medicine has no effective treatment, but homeopathy developed an exceptional reputation for treating yellow fever during the nineteenth century epidemics. In 1878 a devastating yellow fever epidemic occurred in New Orleans and the Mississippi valley. During the epidemic the overall case fatality rate was at least 16 percent (Coulter, 1982). Homeopathically treated cases had a mortality rate of 5.6 percent in New Orleans and 7.7 percent throughout the South (American Institute of Homeopathy, 1880).
Live attenuated yellow fever vaccines have been in use since 1927. Most studies of vaccine effectiveness were conducted in the 1930s. In one study of 60,000 people the vaccine proved to be 95 percent effective in producing antibodies (Smith et al. 1938). In the period 1938-1942 in Colombia, only one case of yellow fever occurred in a population where 127,000 vaccinations were given annually (Bugher & Gast-Galvis, 1944). However, a more recent study showed only that only 75 percent of vaccinated children in Brazil developed adequate antibodies (Guerra et al., 1997). Vaccine ReactionsSevere reactions to the vaccine sometimes occur, especially in children and elderly travelers who receive the vaccine. These reactions are typically characterized by encephalitis. Most cases of vaccine-associated encephalitis have occurred in infants. Prior to 1956 there were 15 cases of encephalitis published in the world literature (Stuart, 1956). A mass vaccination campaign for yellow fever in Senegal during 1965 resulted in 248 cases of vaccine-associated encephalitis. Children under 12 years of age constituted 90 percent of cases. A total of 67 percent had convulsions, 34 percent suffered coma, and 23 cases died (Collomb et al., 1966). Between 1965 and 1991 six cases of encephalitis were reported. Then during the period 1996-2001 five people aged 56-79 years (four US residents and one Australian), and two Brazilians aged 5 and 22 years became ill after receiving yellow fever vaccine. Six of the seven died (CDC, 2001d). Requirements for TravelMore than 100 countries require evidence of yellow fever vaccination for entry. Many countries in Africa and French Guiana in South America require a yellow fever vaccination certificate for entry by anyone. Other countries in Africa, South America, Asia, Europe, the Caribbean, the South Pacific, and the Middle East require a yellow fever certificate for travelers arriving from areas where yellow fever is endemic. For a complete list of the current requirements, see the CDC website at www.cdc.gov/travel/yelfever.htm or contact your state health department.
Vaccine is obtained from Yellow Fever Vaccine Centers designated by state health departments. The vaccine’s protection is presumed to persist for at least 10 years, and a yellow fever certificate is also valid for 10 years.
Those who cannot receive the vaccine for medical reasons can obtain a medical waiver. A valid medical reason includes allergy to eggs, or any immunocompromised condition. The CDC recommends obtaining written waivers from consular or embassy officials before departure.
Yellow Fever Facts
·Yellow fever is present in tropical areas of Africa and South America.
·It is transmitted by mosquito bites.
·Severe reactions to the vaccine have occurred.
·More than 100 countries require vaccination for entry for some travelers, but a medical exemption is available.