Varivax is a vaccine specifically designed to protect against varicella (chickenpox), a contagious viral infection caused by the varicella-zoster virus (VZV). It is a live attenuated vaccine that contains a weakened version of the varicella virus, which stimulates the immune system to develop immunity without causing the actual disease. Varivax is primarily used in children but can also be administered to adults who have not had chickenpox or who have not been vaccinated. It is given through a subcutaneous injection.

Pharmaceutical Properties:

• Formulation: Varivax is available as a lyophilized (freeze-dried) powder that is reconstituted with the accompanying diluent before administration.

• Components: The vaccine contains live, attenuated varicella-zoster virus.

• Adjuvants: It does not contain any additional adjuvants, as the live virus itself is sufficient to stimulate an immune response.

• Storage: Varivax should be stored in a freezer between -15°C and -50°C. Once reconstituted, the vaccine must be used within 30 minutes and cannot be stored.

• Stability: The vaccine is stable when stored correctly before reconstitution. After reconstitution, it must be used immediately.

Indications for Use:

• Primary Prevention of Chickenpox: Varivax is primarily indicated for the prevention of chickenpox in individuals who have not been previously infected with varicella or who have not received the vaccine.

  • Children: The vaccine is recommended for children aged 12 months and older. It is typically administered as a two-dose series: the first dose at 12–15 months of age and the second dose between 4–6 years of age.

  • Adults: Adults who have never had chickenpox and have not been vaccinated may also receive Varivax. In adults, the vaccine may be particularly beneficial in preventing more severe cases of chickenpox, which can be more problematic in this age group.

• Catch-Up Vaccination: Varivax is also used as a catch-up vaccine for children and adults who missed the primary series of varicella vaccination.

• Protection Against Shingles: While primarily intended for chickenpox, vaccination with Varivax may reduce the risk of developing shingles (herpes zoster) later in life by providing long-term immunity to the varicella-zoster virus.

Mechanism of Action:

Varivax works by introducing a weakened (attenuated) form of the varicella-zoster virus into the body. Although this virus is not capable of causing the disease, it stimulates the immune system to produce an immune response. The immune system generates antibodies that can recognize and fight off the virus if the person is exposed to it in the future.

After receiving the vaccine, the body develops long-lasting immunity, which typically prevents the person from contracting chickenpox or reduces the severity of the infection if they are exposed. In addition, the vaccine may also help reduce the likelihood of shingles, which occurs when the varicella-zoster virus reactivates later in life.

Clinical Protocol in Dubai:

In Dubai, vaccination protocols for Varivax align with the standard immunization schedule, as recommended by the Dubai Health Authority (DHA). The vaccination process is as follows:

1. Administration Schedule:

   • First Dose: The first dose of Varivax is administered to children at 12–15 months of age.

   • Second Dose: A second dose is administered between 4 and 6 years of age, typically before school entry.

   • Catch-Up Vaccination: For individuals who missed their first dose, Varivax can be administered to those as young as 12 months, with the second dose given 3 months later. For those older than 13 years who are not previously vaccinated or have not had chickenpox, the vaccine schedule consists of two doses, given 4 to 8 weeks apart.

2. Post-Vaccination Monitoring: After vaccination, it is important to monitor individuals for 15 minutes to detect any allergic reactions or side effects, though severe reactions are rare. Common side effects include mild fever, rash, or soreness at the injection site.

3. Contraindications: Varivax should not be administered to individuals with severe allergic reactions to any component of the vaccine. It should also be avoided by individuals who are immunocompromised, including those undergoing chemotherapy or who are living with HIV/AIDS, unless otherwise directed by a healthcare provider.

4. Precautions: Pregnant women should avoid receiving Varivax. The vaccine is also contraindicated in individuals with a history of anaphylaxis to neomycin (a component of the vaccine) or gelatin.

Other Characteristics:

• Storage: Varivax must be stored in a freezer between -15°C and -50°C prior to reconstitution. After reconstitution, it should be used immediately and not stored.

• Shelf Life: The vaccine has a shelf life of 36 months when stored properly before reconstitution. After reconstitution, it must be used within 30 minutes.

Conclusion:

Varivax is a highly effective vaccine for preventing chickenpox and reducing the risk of shingles. It is an essential tool in childhood immunization programs and offers protection against one of the most common childhood illnesses. By preventing varicella infection, Varivax also helps reduce the risk of complications associated with chickenpox, such as pneumonia and secondary bacterial infections. In Dubai, the vaccine follows the DHA guidelines and is an important part of the public health strategy to reduce the incidence of chickenpox and related complications. Overall, Varivax plays a crucial role in ensuring the health and safety of individuals in both childhood and adulthood.