Moderna begins study for omicron-specific booster shot

Omicron accounts for 99.9% of new COVID-19 cases

Moderna Inc. announced Wednesday that it had begun its first study of an omicron-specific booster dose of its COVID-19 vaccine.

The biotechnology company said the Phase 2 study of its omicron-specific booster candidate – an extension of an earlier study – would include two trials, including one with participants who received its two-dose primary series of the vaccine at least six months ago and another with participants who received that series and a booster dose at least three months ago.


The study will evaluate the safety, immunogenicity and reactogenicity of mRNA-1273.529 as a single booster dose in adults aged 18 years and older, which both trials will receive.

The vaccine-maker said it expects to enroll approximately 300 participants into each cohort, which will be conducted at as many as 24 sites.

Moderna noted that it was evaluating the inclusion of mRNA-1273.529 in its multivalent booster program.

Moderna booster vaccine

Dr. Salma Elfaki holds a vial of Moderna COVID-19 vaccine at a clinical trial for adolescents in Orlando, Florida, on Sept. 25, 2021. (Paul Hennessy/SOPA Images/LightRocket via Getty Images)

In addition, the company wrote that while a booster dose of its original vaccine increased neutralizing antibodies against omicron at the lower dose, their levels declined after a period of six months.

The research, published in The New England Journal of Medicine, said that while omicron neutralization had declined 6.3-fold from peak titers at day 29 post-boost, levels remained detectable in all participants. 

Titer laboratory tests measure the presence and amount of antibodies in the blood, according to George Mason University.


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"Neutralizing titers against omicron declined more rapidly than titers against the ancestral strain of the virus (D614G), which declined 2.3-fold over the same time period," Moderna said in a news release.

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

Seven months following the second dose before the third booster dose, omicron neutralization was detected in just over half of the participants. 

A booster dose of mRNA-1273 at the 50 microgram dose level increased omicron geometric mean titers to 20-fold higher than peak omicron titers after a second dose. 

Neutralizing titers against the variant declined faster after the booster than for the wild-type virus and a 100 microgram booster dose of mRNA-1273, mRNA-1273.211 or mRNA-1273.213 led to neutralizing titers 2.5-2.6-fold higher than those after the 50 microgram booster dose of mRNA-1273.

"We are reassured by the antibody persistence against omicron at six months after the currently authorized 50 [microgram] booster of mRNA-1273. Nonetheless, 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," Stéphane Bancel, Moderna CEO, said in a statement. "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," he added.

Moderna's news comes just a day after Pfizer and BioNTech said they would initiate studies to evaluate omicron-based COVID-19 vaccine candidate in adults ages 18 to 55.