Vaccines for mosquito-borne diseases

Main

Vaccines for mosquito-borne diseases are biological preparations that stimulate the immune system to protect against viral infections transmitted by mosquitoes. These include approved vaccines against yellow fever, Japanese encephalitis, dengue (CYD-TDV), and most recently, chikungunya.

However, there are currently no approved vaccines for other prevalent mosquito-borne diseases like Zika and West Nile virus, although several candidates are in various stages of development.

These vaccines contain weakened or inactivated viruses, viral components, or DNA that encode viral antigens. When administered, they trigger an immune response, leading to the production of antibodies and memory cells that can quickly recognize and fight off future infections. For example, the yellow fever 17D vaccine is a live attenuated vaccine given as a single shot, providing lifelong protection.

Terms

• Antibody: A protein produced by the immune system that recognizes and binds to specific antigens, such as viruses, to neutralize them. Example: Neutralizing antibodies against the Zika virus.

• Antigen: A substance, such as a virus or viral protein, that triggers an immune response when introduced into the body. Example: The envelope protein of the dengue virus.

• Attenuated vaccine: A vaccine containing weakened live viruses that can still replicate but do not cause disease. Example: The yellow fever 17D vaccine.

• Inactivated vaccine: A vaccine containing killed viruses that cannot replicate but still stimulate an immune response. Example: The Japanese encephalitis vaccine.

• Mosquito-borne diseases: Infectious diseases transmitted by mosquitoes, including viral diseases such as dengue, Zika, yellow fever, Japanese encephalitis, chikungunya, and West Nile virus, as well as parasitic diseases like malaria. Example: Dengue fever, caused by the dengue virus and transmitted by Aedes mosquitoes.

• Vaccine: A biological preparation that stimulates the immune system to protect against infectious diseases. Example: The CYD-TDV dengue vaccine.

Analogy

Vaccines for mosquito-borne diseases are like giving your body's defense system a wanted poster of the virus. The vaccine shows your immune cells what the virus looks like, so they can recognize it quickly and take it down before it causes trouble. It's similar to how the police might circulate a picture of a criminal, so officers can spot and apprehend them more easily. For instance, the yellow fever vaccine is like showing your immune system a photo of the yellow fever virus, so it's prepared to fight off the real thing if it ever shows up.

Misconception

A common misconception about vaccines for mosquito-borne diseases is that they can cause the illness they are designed to prevent. Some people believe that because these vaccines contain viral material, they might actually infect them with the virus. However, this is not true. The viruses in these vaccines are either significantly weakened or completely inactivated, meaning they cannot cause disease. For example, some people feared that the dengue vaccine could give them dengue, but clinical trials proved that the vaccine was safe and effective.

History

1. 1932: The first yellow fever vaccine, developed by Max Theiler, is used to protect laboratory workers.

2. 1945: The yellow fever 17D vaccine is licensed and becomes widely used.

3. 1981: The first inactivated Japanese encephalitis vaccine is licensed in Japan.

4. 1995: The live attenuated SA14-14-2 Japanese encephalitis vaccine is licensed in China.

5. 2015: The CYD-TDV dengue vaccine (Dengvaxia) is approved in several countries.

6. 2019-2021: Several Zika virus vaccine candidates enter clinical trials, with promising results in terms of safety and immunogenicity.

7. 2024: A universal mosquito vaccine targeting mosquito saliva proteins shows promise in early clinical trials, potentially offering broad protection against multiple mosquito-borne diseases.

How to use it

1. Sarah is traveling to Brazil, where yellow fever is a risk. She visits her doctor, who recommends the yellow fever vaccine. Sarah receives a single shot at least 10 days before her trip and is protected against the disease.

2. Liam lives in an area where Japanese encephalitis is endemic. As part of the childhood vaccination schedule, he receives two doses of the inactivated vaccine, 28 days apart, at 12-23 months of age. This protects him during the high-risk years of childhood.

3. Olivia is considering the dengue vaccine for her child. After a discussion with her pediatrician and confirming her child has had a previous dengue infection, they proceed with the three-dose series over 12 months. Her child is now protected against severe dengue.

Facts

• The first successful yellow fever vaccine, developed in the 1930s, has been used to immunize over 500 million people worldwide.

• The Japanese encephalitis vaccine is part of the national immunization program in 11 countries, significantly reducing the incidence of this disease.

• As of 2024, there are no licensed vaccines for Zika virus, but 12 candidates are in clinical trials.

• The CYD-TDV dengue vaccine is only recommended for individuals with confirmed prior dengue virus infection, as it may increase the risk of severe dengue in those not previously infected.

• Mosquito-borne diseases affect over 700 million people annually, causing more than 1 million deaths, mostly in tropical and subtropical regions.