Can monovalent (single-valent) formulations be used?

Can Monovalent COVID-19 Vaccines Be Used?

No, monovalent COVID-19 vaccine boosters should not be used for individuals aged ≥12 years, as the FDA has removed the Emergency Use Authorizations (EUAs) for mRNA monovalent COVID-19 vaccine booster doses, and ACIP has repealed its previous recommendations for monovalent boosters. 1

Current Vaccination Recommendations

All individuals aged ≥6 months should receive the 2024-2025 COVID-19 vaccine formulations, which are updated monovalent vaccines targeting current Omicron variants (JN.1-line, including JN.1 and KP.2). 2, 3

Available Vaccine Options for 2024-2025:

• Moderna (monovalent, KP.2-strain) 3
• Pfizer-BioNTech (monovalent, KP.2-strain) 3
• Novavax (monovalent, JN.1-strain) for individuals ≥12 years 3

Dosing Schedule:

• Minimum interval of 8 weeks between the last COVID-19 vaccine dose and the 2024-2025 vaccination 3
• Single dose of 2024-2025 vaccine is recommended for individuals who have already received at least one prior COVID-19 vaccine dose 3

Special Circumstances Where Older Monovalent Formulations May Apply

Novavax Monovalent Booster Exception:

Adults aged ≥18 years who cannot or will not receive mRNA vaccines may use the Novavax monovalent booster if they meet ALL of the following criteria: 2

• Completed any FDA-approved or FDA-authorized primary series
• Have not received any booster doses
• Are unable or unwilling to receive an mRNA vaccine

Historical Context: Why Monovalent Boosters Were Replaced

Monovalent vaccine formulations demonstrated substantially lower effectiveness against Omicron variants compared to earlier variants, with protection waning significantly over time. 4, 5

Evidence of Reduced Effectiveness:

• Monovalent vaccine effectiveness against hospitalization during BA.4/BA.5 period was 49% at 14-149 days after dose 3, declining to 34% at ≥150 days 4
• For children aged 5-11 years, effectiveness against ED/urgent care visits was 51% at 14-59 days after dose 2, declining to 18% at ≥150 days 4
• The protective effect of monovalent vaccination was less pronounced during Omicron than during Delta periods 5

Comparative Effectiveness:

Real-world studies showed monovalent boosters provided moderate protection, with effectiveness of 54% for BNT162b2 and 58% for mRNA-1273 against any medically diagnosed COVID-19, and 70-76% against hospital/ED-diagnosed COVID-19. 6 However, bivalent and updated monovalent formulations targeting current variants are now the standard of care. 1, 2

Common Pitfalls to Avoid

• Do not administer old monovalent booster formulations when updated 2024-2025 vaccines are available and indicated 1, 2
• Do not delay vaccination beyond recommended timeframes (8 weeks after last dose), as this prolongs suboptimal protection 2, 3
• Do not use Janssen (Johnson & Johnson) vaccine except in very limited situations due to thrombosis with thrombocytopenia syndrome risk 2, 3
• Consider delaying vaccination by 3 months if the individual recently had SARS-CoV-2 infection to allow natural immune response to mature 3, 4

Immunocompromised Patients

Immunocompromised individuals require special vaccination considerations, including possible additional doses beyond the standard recommendations. 2, 3 These patients should follow specific ACIP guidelines for their immunocompromised status rather than standard dosing schedules.