On Oct. 13, 2022, Pfizer and BioNTech announced early data from a Phase 2/3 clinical trial (NCT05472038) evaluating the safety, tolerability, and immunogenicity of the companies’ Omicron BA.4/BA.5-adapted bivalent COVID-19 vaccine (Pfizer-BioNTech COVID-19 Vaccine, Bivalent (Original and Omicron BA.4/BA.5)). A 30-µg booster dose of the Omicron BA.4/BA.5-adapted bivalent vaccine demonstrated a substantial increase in the Omicron BA.4/BA.5 neutralizing antibody response above pre-booster levels based on sera taken 7 days after administration, with similar responses seen across individuals aged 18 to 55 years of age and those older than 55 years of age (40 participants in each age group).

When comparing responses in individuals older than 55 years of age who received either the bivalent vaccine, or the original vaccine, a 30-µg booster dose of the Original Pfizer-BioNTech COVID-19 Vaccine (also referred to as BNT162b2 Wild Type) elicited more limited increases in the neutralizing antibody response against the Omicron BA.4/BA.5 variants. COVID-19 vaccine responses to date have reliably shown consistent trends across age groups and are further supported by these early data on the bivalent vaccine. Together, these data suggest a 30-µg booster dose of the Omicron BA.4/BA.5-adapted bivalent vaccine is anticipated to provide better protection against the Omicron BA.4 and BA.5 variants than the original vaccine for younger and older adults. The Omicron BA.4 and BA.5-adapted bivalent vaccine was well tolerated with early data indicating a favorable safety profile, similar to that of the original vaccine.

Immunogenicity was evaluated using a SARS-CoV-2 live virus fluorescent focus reduction neutralization test (FFRNT) assay. Sera were collected 7 days post second booster dose from participants aged older than 55 (40 participants in each age group) and compared to 7-day post sera from 40 participants older than 55 years of age that had received three prior doses of BNT162b2 encoding the wild-type spike-protein of SARS-CoV-2 and a second booster with BNT162b2 Wild-Type. Sera were also collected at 7 days post second booster dose from participants 18 to 55 years of age who received the Omicron BA.4/BA.5-adapted bivalent booster (n=40) to compare bivalent vaccine responses in younger and older adults. The time between third and fourth doses for the bivalent vaccine recipients was approximately 11 months compared to approximately 6 months for the original vaccine. Despite this difference, baseline neutralizing antibody titers were generally similar across groups. Among the participants, samples were equally stratified at baseline in each group between those who had a prior or current history of SARS-CoV-2 and those with no prior or current history of SARS-CoV-2.

Additional data measuring responses at one-month post-administration of the Omicron BA.4/BA.5 bivalent vaccine booster are expected in the coming weeks. These data will be used to support potential full licensure and global registration of the companies’ Omicron BA.4/BA.5-adapted bivalent COVID-19 vaccine. Additionally, the companies have initiated a similar Phase 1/2/3 trial (NCT05543616) investigating the Omicron BA.4/BA.5-adapted bivalent vaccine among children 6 months through 11 years of age.

A 30-µg booster dose of the Omicron BA.4/BA.5-adapted bivalent vaccine has been authorized for emergency use by the U.S. Food and Drug Administration (FDA) for ages 12 years and older and has also been granted marketing authorization in the EU by the European Medicines Agency (EMA) for the same age group.