This week the companies have published laboratory data showing that three doses of the current formulation elicit antibodies that neutralize the Omicron variant.
However, the companies are evaluating both the current formulation and an Omicron-based vaccine in clinical trials: with participants receiving up to four doses in total.
Clinical trials under way
Today, the companies announced a set of clinical trials evaluating up to 1,420 participants aged 18-55.
Three cohorts will investigate efficacy as follows:
- Cohort #1 (n = 615): Having received two doses of the current Pfizer-BioNTech COVID-19 vaccine 90-180 days prior to enrollment; participants will receive one or two doses of the Omicron-based vaccine
- Cohort #2 (n = 600): Having received three doses of the current Pfizer-BioNTech COVID-19 vaccine 90-180 days prior to enrollment; participants will receive one dose of the current Pfizer-BioNTech COVID-19 vaccine or the Omicron-based vaccine
- Cohort #3 (n=205): Vaccine-naïve participants will receive three doses of the Omicron-based vaccine
“While current research and real-world data show that boosters continue to provide a high level of protection against severe disease and hospitalization with Omicron, we recognize the need to be prepared in the event this protection wanes over time and to potentially help address Omicron and new variants in the future,” said Kathrin U. Jansen, Ph.D., Senior Vice President and Head of Vaccine Research & Development at Pfizer.
“Staying vigilant against the virus requires us to identify new approaches for people to maintain a high level of protection, and we believe developing and investigating variant-based vaccines are essential in our efforts to towards this goal.”
Since Omicron emerged in December, vaccine developers have been working on evaluating the efficacy of existing COVID-19 vaccines as well as developing variant-specific versions.
Early findings suggest that existing vaccines do provide protection, although the level of protection may change or be dependent on the number of doses. As with Pfizer/BioNTech, vaccine developers such as J&J, Moderna, and Valneva have issued positive data.
Pfizer expects an Omicron-specific vaccine will be ready in March; although it has not commented on the regulatory steps the vaccine is likely to have to go through (FDA leaders have cautioned that such a vaccine may not be necessary.)
Other developers, such as Moderna, are also working on variant-specific vaccines.
Efficacy of vaccines
On Monday, Pfizer and BioNTech announced the publication of two laboratory studies showing that three doses of their current COVID-19 vaccine elicit antibodies which neutralize the Omicron variant.
Published in the peer-reviewed journal Science, the first study includes readouts of sera data from 51 vaccinated individuals that received two or three doses of BNT162b2; which a second evaluated the neutralization potential of serum antibodies from a subset of vaccinated individuals against the live virus.
Serum antibodies induced by BNT162b2 neutralized the SARS-CoV-2 Omicron variant after immunization with three doses. In comparison, sera from individuals who received two doses of the COVID-19 vaccine revealed limited neutralization titers against the Omicron variant: suggesting that two doses ‘may not be sufficient to protect against infection’ with the variant.
However, based on observations that around 85% of epitopes in the spike protein recognized by CD8+ T cells are not affected by the mutations in the Omicron variant, the companies believe two doses may still induce protection against severe disease.
The results support those from an initial study released by the companies in December.
University of Texas study
A separate live virus laboratory study conducted with the University of Texas Medical Branch (UTMB) showed sera taken 1-month following a third dose showed a 22-fold increase in neutralization titers against Omicron compared to titers just prior to the third dose (7.9 to 8.8 months after second dose), suggesting more robust protection against the new variant may be achieved with the current COVID-19 vaccine series plus a booster dose.
Additionally, the neutralizing titer levels against Omicron after immunization with three doses were similar to antibody titer levels after two doses against wild-type and other variants that emerged before Omicron. Further, from 1 to 4 months after a third dose, neutralization titers against wild-type and Omicron decreased by 1.6 and 2.0 times, respectively, suggesting similar waning for both variants. All sera effectively neutralized Omicron at 4 months following a third dose.
These findings have been posted on the preprint server bioRxiv.