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Safety and Immunogenicity of a Third Dose of SARS-CoV-2 mRNA Vaccine - An Interim Analysis
Evan Anderson, Lisa Jackson1, Nadine Rouphael2
1Kaiser Permanente Washington Health Research Institute.
Abstract:
Waning immunity after two SARS-CoV-2 mRNA vaccinations and the emergence of variants precipitated the need for a third dose of vaccine. We evaluated early safety and immunogenicity after a third mRNA vaccination in adults who received the mRNA-1273 primary series in the Phase 1 trial approximately 9 to 10 months earlier. The booster vaccine formulations included 100 mcg of mRNA-1273, 50 mcg of mRNA-1273.351 that encodes Beta variant spike protein, and bivalent vaccine of 25 mcg each of mRNA-1273 and mRNA-1273.351. A third dose of mRNA vaccine appeared safe with acceptable reactogenicity. Vaccination induced rapid increases in binding and neutralizing antibody titers to D614G, Beta, and Delta variants that were similar or greater than peak responses after the second dose. Spike-specific CD4+ and CD8+ T cells increased to similar levels as after the second dose. A third mRNA vaccination was well tolerated and generated robust humoral and T cell responses. ClinicalTrials.gov numbers NCT04283461 (mRNA-1273 Phase 1) and NCT04785144 (mRNA-1273.351 Phase 1).
Insights
A third mRNA vaccine dose safely boosted immunity against SARS-CoV-2 variants. This booster generated strong antibody and T cell responses, similar to or exceeding those after the primary vaccination series.
Area of Science:
- Immunology
- Vaccinology
- Virology
Background:
- Waning immunity following two SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) mRNA vaccinations necessitated a third dose.
- Emergence of SARS-CoV-2 variants further underscored the need for enhanced vaccine efficacy.
Approach:
- Evaluated early safety and immunogenicity of a third mRNA vaccine dose in adults previously receiving the mRNA-1273 primary series.
- Tested booster formulations: 100 mcg mRNA-1273, 50 mcg mRNA-1273.351 (Beta variant spike protein), and a bivalent 50 mcg vaccine (25 mcg each of mRNA-1273 and mRNA-1273.351).
Key Points:
- Third mRNA vaccination demonstrated acceptable safety and reactogenicity.
- Antibody titers against D614G, Beta, and Delta variants increased rapidly post-booster, reaching levels similar to or greater than peak responses after the second dose.
- Spike-specific CD4+ and CD8+ T cell responses also increased to levels comparable to those after the primary series.
Conclusions:
- A third mRNA vaccination is well-tolerated.
- The booster dose elicits robust humoral and cellular immune responses.
- This supports the use of third mRNA vaccine doses to combat waning immunity and emerging SARS-CoV-2 variants.
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