In June 2023, the FDA’s VRBPAC met and voted to recommend that all COVID-19 vaccines manufactured for use in the United States be updated to target the Omicron XBB strain, with a preference for the XBB.1.5 strain. The FDA advised COVID-19 vaccine manufacturers that they should develop a monovalent COVID-19 vaccine to specifically target the XBB.1.5 strain for use in 2023-2024.
On September 11, 2023, the FDA approved use of the Pfizer-BioNTech Comirnaty and the Moderna SPIKEVAX 2023-2024 COVID-19 vaccines containing the SARS-CoV-2 Omicron variant XBB.1.5 for use in individuals aged 12 year of age and older. The FDA also authorized use of a 3mcg dose of Pfizer-BioNTech 2023-2024 COVID-19 vaccine for use in children aged 6 months through four years of age, a 10mcg dose of Pfizer-BioNTech 2023-2024 COVID-19 vaccine for use in children aged five through 11 years of age, and a 25 mcg dose of Moderna 2023-2024 COVID-19 vaccine for use in children aged 6 months through 11 years of age. One day later, the CDC recommended use of the vaccines for all persons six months of age and older.
Approval for the vaccines manufactured and distributed by Pfizer-BioNTech was based on safety and efficacy data from clinical trials completed for COVID-19 vaccines containing the original SARS-CoV-2 virus and on trials of an experimental COVID-19 vaccine containing the original SARS-CoV-2 and Omicron variant BA.1.
No human clinical trials were conducted on the Pfizer-BioNTech 2023-2024 COVID-19 vaccines prior to the September 11, 2023 FDA approval and authorizations. Pfizer-BioNTech company officials, however, reported that the vaccine elicited immune responses when tested on 20 female mice.
The FDA approved and authorized the Moderna 2023-2024 mRNA COVID-19 vaccines based on safety and efficacy data from clinical trials completed on the COVID-19 vaccines containing the original SARS-CoV-2 virus and on trials of an experimental COVID-19 vaccine containing the original SARS-CoV-2 and Omicron variant BA.1.
Additionally, Moderna conducted a clinical trial involving 101 individuals previously vaccinated with 3 doses of the original monovalent COVID-19 vaccine and one dose of bivalent COVID-19 vaccine. Fifty adult participants received a 50 mcg dose of a monovalent COVID-19 vaccine containing the SARS-CoV-2 Omicron variant XBB.1.5 and fifty-one participants received a dose of a bivalent COVID-19 vaccine containing 25mcg of SARS-CoV-2 Omicron XBB.1.5 variant and 25mcg of Omicron BA.4/BA.5.
According to the data published by company officials, fifteen days after receipt of the vaccine, individuals who received the monovalent COVID-19 vaccine containing SARS-CoV-2 Omicron variant XBB.1.5 had higher antibody response against the original SARS-CoV-2 virus, and the Omicron XBB.1.5 and Omicron XBB.1.16 variant than those who received the experimental bivalent booster. Most clinical trial participants reported both localized and system adverse reactions following vaccination. Researchers reported that no serious adverse events or deaths occurred among trial participants, however, data was limited to only 20-22 days post vaccination.
The FDA issued an EUA to Novavax for its adjuvanted COVID-19 vaccine containing spike protein from the Omicron XBB.1.5 variant of SARS-CoV-2 on October 3, 2023. No clinical trials of this vaccine were conducted prior to FDA authorization. Instead, federal regulators stated that the authorization of this updated vaccine was based on safety and effectiveness data from the original Novavax COVID-19 vaccine clinical trials and an experimental monovalent and bivalent Novavax vaccine, along with post-marketing data. The FDA justified the use of data from different vaccine products by stating that “the data accrued with these Novavax COVID-19 vaccines are relevant to Novavax COVID-19 Vaccine, Adjuvanted (2023-2024 Formula) as the vaccines are manufactured using a similar process.”
No human trials were conducted on the Novavax COVID-19 vaccine targeting Omicron XBB.1.5. Novavax company officials, however, reported that this vaccine produced “robust neutralizing responses against XBB subvariants” in rhesus macaques.
The FDA revoked the EUA for the original Novavax COVID-19 vaccine when it authorized use of the Novavax COVID-19 vaccine containing the Omicron XBB.1.5 variant.
