This week, both Moderna and Pfizer announced they have commenced clinical trials testing Omicron-specific formulations of their mRNA COVID-19 vaccines. Data from the trials is expected in the first half of 2022, however, some experts suggest the end of the year may be too late to deliver Omicron vaccines as it is possible we will be facing new and different variants by that time.
Pfizer and BioNTech were first to announce the initiation of large clinical trials testing an Omicron-specific mRNA vaccine earlier this week. The plan is to enroll 1,420 participants spread across three cohorts.
The largest cohort (615 subjects) will investigate the safety and immunogenicity of the Omicron-specific vaccine in those who have received two doses of the standard Pfizer COVID-19 vaccine. A second cohort of 600 subjects who have received three doses of the standard mRNA vaccine will either receive a fourth dose of the Omicron-specific formulation or the original formulation. Again, the research will measure safety and immune responses in the cohort.
A third smaller cohort of around 200 unvaccinated subjects will be recruited to test a complete three-dose protocol of the Omicron-specific vaccine.
“Vaccines continue to offer strong protection against severe disease caused by Omicron," said CEO of BioNTech, Ugur Sahin. "Yet, emerging data indicate vaccine-induced protection against infection and mild to moderate disease wanes more rapidly than was observed with prior strains. This study is part of our science-based approach to develop a variant-based vaccine that achieves a similar level of protection against Omicron as it did with earlier variants but with longer duration of protection.”
Quickly following Pfizer’s announcement, Moderna responded with news of its own Omicron-specific clinical trial. It will focus on two cohorts of 300 subjects each. One group will test the effects of Moderna’s Omicron-specific formulation as a third dose administered at least six months after the two-dose primary protocol. A second group with test the Omicron vaccine as a fourth dose given at least three months after the third booster dose.
Stéphane Bancel, CEO of Moderna, said the data generated by this trial will inform booster programs later in the year.
“… given the long-term threat demonstrated by Omicron's immune escape, we are advancing our Omicron-specific variant vaccine booster candidate and we are pleased to begin this part of our Phase 2 study," said Bancel. "We are also evaluating whether to include this Omicron-specific candidate in our multivalent booster program. We will continue to share data with public health authorities to help them make evidence-based decisions on the best booster strategies against SARS-CoV-2."
With third-dose COVID-19 vaccine programs currently underway across the world the big question is when will a fourth vaccine dose be necessary? Both Pfizer and Moderna’s clinical research is likely to take months to deliver results so no large-scale roll-out of an Omicron-specific vaccine could be reasonably expected until later in 2022.
Early in January, Moderna CEO Bancel did indicate a fourth vaccine dose is expected to be necessary before the Northern Hemisphere winter later in 2022. But with the incredible pace of mutations SARS-CoV-2 seems to be accumulating it is unclear whether an Omicron-specific variant will be particularly useful in six to 12 months time.
Australian researcher Deborah Burnett, from the Garvan Institute, recently argued variant-specific vaccines may be a futile and reactive strategy considering the sheer pace at which new viral variants can appear and spread. Burnett said a variant-proof universal COVID-19 vaccine targeted at a number of parts of SARS-CoV-2 is more likely the better long-term plan.
“… variant-specific vaccines are ultimately a reactive measure that could always leave us behind the eight ball,” Burnett wrote in a recent piece for The Conversation. “By the time we roll out any variant-specific vaccine, a wave of infections driven by that variant may already have peaked, and a new variant will likely be on the way. The solution to this problem may be 'variant-proof' vaccines, also known as 'universal' COVID vaccines. These are vaccines which work across different variants, rather than being targeted to a specific variant.”
