Why is there an option for immunocompromised people to receive additional COVID-19 vaccine doses?

Individuals with moderate to severe immunocompromise who have completed a primary series should receive one dose of 2024–2025 Formula COVID-19 vaccine this season followed by a second dose 6 months (minimum 2 months) later. Additional doses of 2024–2025 Formula COVID-19 vaccine may be administered (with a minimum two-month interval) based on the clinical judgment of the individual’s healthcare provider and the recipient’s personal preference and circumstances. 

The option to receive additional doses is offered because COVID-19 vaccine effectiveness declines most rapidly in people with moderate to severe immunocompromise. Such people also have the highest risk of hospitalization with COVID-19 if infected. Although protection against severe disease is more durable than protection against milder illness, individuals in these groups may benefit from shorter intervals between doses.