In a press release, Moderna, one of the manufacturers of the COVID-19 mRNA vaccines, announced preliminary neutralizing antibody data against the Omicron variant following the company's booster candidates at 50-mcg and 100-mcg dose levels. The currently authorized 50-mcg booster of mRNA-1273 increased neutralizing antibody levels against Omicron approximately 37-fold compared with preboost levels, and a 100-mcg dose of mRNA-1273 increased neutralizing antibody levels approximately 83-fold compared with preboost levels.

In the press release, Stéphane Bancel, chief executive officer of Moderna, stated, "The dramatic increase in COVID-19 cases from the Omicron variant is concerning to all. However, these data showing that the currently authorized Moderna COVID-19 booster can boost neutralizing antibody levels 37-fold higher than pre-boost levels are reassuring. To respond to this highly transmissible variant, Moderna will continue to rapidly advance an Omicron-specific booster candidate into clinical testing in case it becomes necessary in the future. We will also continue to generate and share data across our booster strategies with public health authorities to help them make evidence-based decisions on the best vaccination strategies against SARS-CoV-2."

As previously described, the company is continuously advancing booster candidates to address emerging variants of concern (VOC). The strategy includes evaluating the prototype vaccine (mRNA-1273) at the authorized booster dose (50 mcg) and a higher dose (100 mcg), multivalent candidates that incorporate previous VOC (mRNA-1273.211, mRNA-1273.213) also at 50 mcg and 100 mcg, and VOC-specific booster candidates (Delta, Omicron). Booster candidates are being evaluated in ongoing phase II/III studies of approximately 300 to 600 participants per arm.

Data includes sera from 20 booster recipients each of mRNA-1273 at the 50-mcg and 100-mcg dose levels, multivalent candidate mRNA-1273.211 at the 50-mcg and 100-mcg dose levels, and multivalent candidate mRNA-1273.213 at the 100-mcg dose level.

Neutralizing antibodies against Omicron were assessed in a pseudovirus neutralization titer (ID50) assay (PsVNT) conducted at laboratories established by the National Institute of Allergy and Infectious Diseases Vaccine Research Center and Duke University Medical Center. A preprint submission is being prepared based on the data.

All groups had low neutralizing antibody levels in the Omicron PsVNT assay prior to boosting. At Day 29 post boost, the authorized 50-mcg booster of mRNA-1273 increased neutralizing geometric mean titers (GMT) against Omicron to 850, which is approximately 37-fold higher than preboost levels. At Day 29 post boost, the 100-mcg dose booster of mRNA-1273 increased neutralizing GMT to 2228, which is approximately 83-fold higher than preboost levels.

The multivalent candidates boosted Omicron-specific neutralizing antibody levels to similarly high levels at both the 50-mcg and 100-mcg levels. Based on the strength of neutralizing titers generated by mRNA-1273, the rapid pace of Omicron expansion and the increased complexity of deploying a new vaccine, the company will focus its near-term efforts to address Omicron on the mRNA-1273 booster.

Moderna will continue to assess the breadth and durability of neutralizing antibodies from the multivalent booster candidates in the months ahead.

The company also announced the safety and tolerability data from the phase II/III study of the 100-mcg booster dose of mRNA-1273 (n = 305). A 100-mcg booster dose of mRNA-1273 was generally safe and well-tolerated. The frequency and nature of solicited systemic and local adverse events 7 days after receiving a booster were generally comparable with those seen after the two-dose primary series. There was a trend toward slightly more frequent adverse reactions following the 100-mcg booster dose relative to the authorized 50-mcg booster dose of mRNA-1273.

Moving forward, given the strength of the mRNA-1273 and the speed at which the Omicron variant is spreading, Moderna's first line of defense against Omicron will be a booster dose of mRNA-1273. Given the long-term threat demonstrated by Omicron's immune escape, Moderna will also continue to develop an Omicron-specific variant vaccine (mRNA-1273.529) that is expected to advance into clinical trials in early 2022 and will evaluate including Omicron in its multivalent booster program.

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