Preventing varicella: Recommendations for routine two-dose varicella immunization in children

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• One-dose varicella vaccination programs in Canada since 2007 have significantly reduced chickenpox incidence.
• Breakthrough varicella cases persist, with some severe infections observed.
• Waning immunity after a single vaccine dose is a growing concern, potentially shifting severe disease to older age groups.

Purpose of the Study:

• To present the scientific rationale for adopting a two-dose varicella vaccination strategy in Canada.
• To recommend a routine two-dose schedule for all Canadian children to enhance long-term immunity.

Main Methods:

• Review of existing evidence on varicella vaccine effectiveness and waning immunity.
• Analysis of disease trends and complications in vaccinated populations.
• Formulation of recommendations based on scientific data and public health considerations.

Main Results:

• Evidence suggests that a single dose of varicella vaccine may not provide lifelong immunity.
• A shift in disease epidemiology towards older, more vulnerable populations is indicated.
• A two-dose strategy is proposed to address waning immunity and improve population-level protection.

Conclusions:

• A two-dose varicella vaccination schedule is recommended for all Canadian children.
• Children who received one dose and have not had chickenpox should receive a second dose.
• This strategy aims to bolster immunity, reduce breakthrough infections, and mitigate severe disease outcomes.