Varicella (chickenpox) is a highly contagious disease caused by primary infection with varicella-zoster virus (VZV). It occurs worldwide and is usually self-limiting in children, but complications and severe disease can occur. After primary infection, VZV remains latent and may later reactivate as herpes zoster (shingles). 

Countries should base decisions on introduction varicella vaccination into their national immunization programmes on the local disease burden, epidemiology, programme performance, affordability, cost-effectiveness and available resources. Where varicella is an important public health problem and vaccination is introduced, programmes should aim for high and sustained coverage at national and subnational levels. 

• VZV is transmitted mainly through respiratory droplets or aerosols and through direct contact with fluid from skin lesions. 

• Varicella typically causes fever and an itchy vesicular rash. Complications can include bacterial skin and soft-tissue infection, pneumonia and neurological disease. 

• The risk of severe disease is higher in adults, pregnant women, newborns and people who are immunocompromised. 

• Because VZV remains latent after infection, it may subsequently reactivate and cause herpes zoster. 
  
  

Varicella vaccines are live attenuated vaccines. They are available as monovalent products and in combination vaccines containing measles, mumps, rubella and varicella antigens (MMRV). The available varicella vaccines are licensed for administration starting from 9 or 12 months, depending on the product.  

• Countries where varicella represents an important public health problem may consider introducing varicella vaccination into the routine childhood immunization programme, taking account of local priorities and programme feasibility. 

• A two-dose schedule is recommended when a country decides to implement universal childhood varicella vaccination. The first dose may be administered from 9 months of age, with the second dose given according to the national schedule and product information; the minimum interval between doses is 4 weeks. 

• Countries introducing vaccination should aim for high, sustained coverage with both doses at national and subnational levels, supported by appropriate surveillance. 

• Countries considering a one-dose schedule should note that, while such a programme may be sufficient to reduce mortality and severe morbidity from varicella, it is less effective in preventing virus circulation and occasional outbreaks. 

• Catch-up vaccination may be considered for children, adolescents and adults without evidence of immunity, using a two-dose schedule, according to national epidemiology, priorities and resources. 

• For special populations and people with altered immunity, decisions should follow the detailed WHO guidance, product information and an individual clinical assessment because live varicella vaccines are contraindicated in some circumstances.