Yellow fever is a contagious disease caused by the yellow fever virus, transmitted by Aedes mosquitoes from infected patients to healthy individuals, similar to dengue fever. This disease is endemic and commonly found in Africa and South America. It can be prevented by receiving the yellow fever vaccine, which provides immunity for at least 10 years.
Symptoms of Yellow Fever
- Patients will have high fever, headache, muscle pain, nausea, vomiting, bleeding from the mouth or nose, and may vomit or have bloody stools. In the early stage, patients will have mild jaundice (yellowing of the eyes and skin), which becomes more severe in later stages.
- About 50% of patients die within the second week after symptoms begin due to liver failure, kidney failure, and other complications. There is no specific treatment for this disease, so prevention is essential.
Yellow Fever Vaccine
Made from live attenuated yellow fever virus, the vaccine is injected subcutaneously once. After vaccination, immunity lasts for at least 10 years.
Who “Should” Receive the Yellow Fever Vaccine
- Children aged 9 months and older, and adults living in or traveling to areas where yellow fever is endemic. The vaccine should be given at least 10 days before travel.
- Those who have been vaccinated will receive a vaccination certificate, valid from 10 days after vaccination up to 10 years thereafter.
Who “Should Avoid” Receiving the Yellow Fever Vaccine
- Those who have had severe allergic reactions to the yellow fever vaccine previously.
- Those allergic to gelatin or eggs.
- Children under 6 months old.
Possible Side Effects After Receiving the Yellow Fever Vaccine
- Severe allergic reactions to the vaccine are very rare. Common side effects may include pain, swelling, and redness at the injection site, low-grade fever, headache, muscle pain, and fatigue, which may last 5-10 days.
- More severe side effects that occur more frequently include high fever and flu-like symptoms.
- If there is pain and swelling at the injection site, apply a cold compress. For low-grade fever, antipyretics can be taken. If any other abnormal symptoms occur, consult a doctor immediately.
Who “Should Avoid” Traveling to Yellow Fever Endemic Areas
- Adults aged 65 years and older.
- Pregnant and breastfeeding women.
- Children aged 6-9 months.
- Individuals with immunodeficiency, such as those infected with HIV/AIDS.
- Cancer patients or those undergoing cancer treatment, including radiation or chemotherapy.
- Those taking medications that affect the immune system, such as steroids.
- Patients with thymus gland disorders, such as thymus tumors or those who have had thymus surgery.
- If having a fever, vaccination should be postponed until recovery.
- Those with contraindications or health restrictions preventing vaccination must have a medical certificate for travel and follow advice from the embassy of the destination country, including measures to prevent infection and mosquito bites.
Because side effects from the vaccine may cause adverse reactions in these groups, they should avoid traveling to outbreak areas. However, if travel cannot be avoided, vaccination may be given but must be consulted with a doctor beforehand.
Note:
- In addition to vaccination, prevention of yellow fever includes avoiding mosquito bites by using mosquito repellent and wearing protective clothing.
- Travelers coming from yellow fever endemic areas entering Thailand without vaccination certificates must receive the vaccine and report their health status to public health officers at international disease control checkpoints within 6 days from the date of departure from the endemic area.
