Moderna Spikevax BA.4/BA.5 Bivalent Booster Administration
All persons aged ≥5 years should receive a bivalent mRNA COVID-19 vaccine booster dose (Moderna Spikevax BA.4/BA.5) at least 2 months after completion of any FDA-approved primary series or monovalent booster doses. 1, 2, 3
Vaccine Composition and Mechanism
- The Moderna bivalent booster contains 25 μg ancestral mRNA spike protein and 25 μg of Omicron BA.4/BA.5 mRNA spike protein (total = 50 μg) 1, 2
- The mRNA delivers genetic instructions to cells, resulting in temporary expression of both the original and Omicron BA.4/BA.5 spike proteins, triggering antibody and cellular immune responses 2
- The mRNA does not enter the cell nucleus or interact with DNA, and is degraded shortly after protein production 2
Eligibility and Timing
Administer the bivalent booster at least 2 months after the last COVID-19 vaccine dose (whether primary series or monovalent booster). 1, 2, 3
- For persons who recently had SARS-CoV-2 infection, consider delaying the booster dose by 3 months from symptom onset or positive test result 2, 3
- This recommendation applies to all persons aged ≥5 years who completed any FDA-approved or FDA-authorized primary series 1, 2
Administration Technique
Administer intramuscularly at a 90-degree angle into the deltoid muscle of the upper arm for adolescents and adults, or the anterolateral aspect of the thigh for young children. 1, 4
Specific Technical Requirements:
- Use a 22-25 gauge needle, 1-1½ inches in length for adolescents and adults to ensure proper muscle penetration 4
- For children aged 5-11 years, the anterolateral thigh is the preferred site 1
- Never use the buttock for vaccine administration due to risk of sciatic nerve injury and decreased immunogenicity 1, 4
- Insert the needle into the injection site and pull back the plunger—if blood appears, withdraw and select a new site 1
Safety Protocols
Use sterile, disposable needles and syringes for each injection, never reusing or sharing equipment between patients. 1, 4
- Wash hands with soap and water or use alcohol-based hand rub between each patient 1, 4
- Gloves are not required unless the provider will contact potentially infectious body fluids or has open hand lesions 1, 4
- Discard used sharps immediately in labeled, puncture-proof containers without recapping 1, 4
- Never mix different vaccines in the same syringe unless specifically licensed for such use 1, 4
Expected Reactogenicity
Moderate, transient local and systemic reactions occur more frequently with Moderna vaccines and are more common after booster doses than primary series. 5, 6, 7
Common Adverse Events:
- Fatigue, chills, headache, myalgia, and injection site pain are the most frequently reported symptoms 5, 8
- Reactogenicity is dose-dependent and more common in younger adults (30-39 years) and females 6, 8
- Approximately 50.7% of recipients report any adverse event in the first 0-3 days after vaccination 8
- Serious adverse events are rare, with similar incidence to placebo groups in clinical trials 7
Critical Safety Consideration:
Myocarditis is a rare risk after mRNA COVID-19 vaccination, primarily affecting adolescent and young adult males, with highest risk among males aged 16-19 years (137 per million). 2
Clinical Rationale
The bivalent BA.4/BA.5 formulation was developed because monovalent vaccine effectiveness against COVID-19-associated hospitalization declined from 49% at 14-149 days after dose 3 to 34% at ≥150 days during the BA.4/BA.5 period 2, 3. Modeling demonstrates that vaccination coverage similar to influenza vaccine would reduce hospitalizations and deaths by >20% and >15%, respectively 1. The bivalent formulation expands immune protection against currently circulating Omicron variants while maintaining protection against the original strain 2.