Interim analysis of a phase 1 randomized clinical trial on the safety and immunogenicity of the mRNA-1283 SARS-CoV-2 vaccine in adults.

This interim analysis of an ongoing phase 1 randomized clinical trial evaluated the safety, reactogenicity, and immunogenicity of mRNA-1283, a next-generation SARS-CoV-2 messenger RNA (mRNA)-based vaccine encoding two segments of the spike protein (i.e. receptor binding and N-terminal domains). Healthy adults aged 18-55 years (n = 104) were randomized (1:1:1:1:1) to receive two doses of mRNA-1283 (10, 30, or 100 µg) or mRNA-1273 (100 µg) administered 28 days apart, or a single dose of mRNA-1283 (100 µg). Safety was assessed and immunogenicity was measured by serum neutralizing antibody (nAb) or binding antibody (bAb) responses. At the interim analysis, no safety concerns were identified and no serious adverse events, adverse events of special interest, or deaths were reported. Solicited systemic adverse reactions were more frequent with higher dose levels of mRNA-1283 than with mRNA-1273. At day 57, all dose levels of the 2-dose mRNA-1283 regimen (including the lowest dose level [10 µg]) induced robust nAb and bAb responses that were comparable to those of mRNA-1273 (100 µg). mRNA-1283 was generally safe in adults, with all dose levels of the 2-dose regimen (10, 30, and 100 µg) eliciting similar immunogenicity as the 2-dose mRNA-1273 regimen (100 µg).Clinical Trials Registration: Clinicaltrials.gov, NCT04813796.

SARS-CoV-2 Omicron boosting induces de novo B cell response in humans.

The primary two-dose SARS-CoV-2 mRNA vaccine series are strongly immunogenic in humans, but the emergence of highly infectious variants necessitated additional doses and the development of vaccines aimed at the new variants1-4. SARS-CoV-2 booster immunizations in humans primarily recruit pre-existing memory B cells5-9. However, it remains unclear whether the additional doses induce germinal centre reactions whereby re-engaged B cells can further mature, and whether variant-derived vaccines can elicit responses to variant-specific epitopes. Here we show that boosting with an mRNA vaccine against the original monovalent SARS-CoV-2 mRNA vaccine or the bivalent B.1.351 and B.1.617.2 (Beta/Delta) mRNA vaccine induced robust spike-specific germinal centre B cell responses in humans. The germinal centre response persisted for at least eight weeks, leading to significantly more mutated antigen-specific bone marrow plasma cell and memory B cell compartments. Spike-binding monoclonal antibodies derived from memory B cells isolated from individuals boosted with either the original SARS-CoV-2 spike protein, bivalent Beta/Delta vaccine or a monovalent Omicron BA.1-based vaccine predominantly recognized the original SARS-CoV-2 spike protein. Nonetheless, using a more targeted sorting approach, we isolated monoclonal antibodies that recognized the BA.1 spike protein but not the original SARS-CoV-2 spike protein from individuals who received the mRNA-1273.529 booster; these antibodies were less mutated and recognized novel epitopes within the spike protein, suggesting that they originated from naive B cells. Thus, SARS-CoV-2 booster immunizations in humans induce robust germinal centre B cell responses and can generate de novo B cell responses targeting variant-specific epitopes.

Clinical Development of mRNA Vaccines: Challenges and Opportunities.

The emergence of safe and effective mRNA platform-based COVID-19 vaccines from the recent pandemic has changed the face of vaccine development. Compared with conventional technologies used historically, mRNA-based vaccines offer a rapid flexible and robust approach to preventing disease caused by transient viral strains such as SAR2-CoV-2 variants of concern and seasonal influenza. Adaptations in the formulation of the mRNA delivery systems such as with lipid nanoparticle delivery (LNP) used in mRNA-1273 and BNT16b2b have enabled this technology to flourish under the urgent collective response and collaborative regulatory understanding derived from COVID-19 vaccine development. The application of mRNA-based therapeutics in other areas holds potential promise including combination vaccines that might deliver protections against multiple infectious diseases. Future studies and further advances in mRNA-based technologies will provide insight into the clinical efficacy and real-world effectiveness of vaccines as well as provisions with respect to the impact of reactogenicity profiles. Overall, the success of mRNA-based COVID-19 vaccines has helped unlock a platform likely to result in many more candidate vaccines entering clinical evaluation to address the unmet medical needs of other diseases including viral respiratory diseases, herpesviruses, and historically challenging vaccine targets such as HIV.

Humoral Immunogenicity of the mRNA-1273 Vaccine in the Phase 3 Coronavirus Efficacy (COVE) Trial.

BACKGROUND: Messenger RNA (mRNA)-1273 vaccine demonstrated 93.2% efficacy against coronavirus disease 2019 (COVID-19) in the Coronavirus Efficacy (COVE) trial. The humoral immunogenicity results are now reported. METHODS: Participants received 2 mRNA-1273 (100 µg) or placebo injections, 28 days apart. Immune responses were evaluated in a prespecified, randomly selected per-protocol immunogenicity population (n = 272 placebo; n = 1185 mRNA-1273). Serum binding antibodies (bAbs) and neutralizing antibodies (nAbs) to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-spike protein were assessed at days 1, 29, and 57 by baseline SARS-CoV-2-negative (n = 1197) and SARS-CoV-2-positive (n = 260) status, age, and sex. RESULTS: SARS-CoV-2-negative vaccinees had bAb geometric mean AU/mL levels of 35 753 at day 29 that increased to 316 448 at day 57 and nAb inhibitory dilution 50% titers of 55 at day 29 that rose to 1081 at day 57. In SARS-CoV-2-positive vacinees, the first mRNA-1273 injection elicited bAb and nAb levels that were 11-fold (410 049) and 27-fold (1479) higher than in SARS-CoV-2-negative vaccinees, respectively, and were comparable to levels after 2 injections in uninfected participants. Findings were generally consistent by age and sex. CONCLUSIONS: mRNA-1273 elicited robust serologic immune responses across age, sex, and SARS-CoV-2 status, consistent with its high COVID-19 efficacy. Higher immune responses in those previously infected support a booster-type effect. Clinical Trials Registration. NCT04470427.