As regulatory agencies gear up for another round of Covid-19 vaccine deliberations centered on emerging variants, Moderna has released data on its booster’s efficacy against Omicron subvariants.

In addition to providing protection against the Omicron BA.1 variant, on 22 June, Moderna said its booster also showed a “potent” antibody response against Omicron subvariants BA.4 and BA.5. The mRNA-1273.214 booster contains the original Spikevax vaccine and a candidate targeting Omicron BA.1 variant of concern.

Even though the Omicron strain BA.1 is slightly different from the currently circulating ones, such as BA.4 and BA.5, there may be enough overlap for the bivalent vaccine to offer protection against all the subvariants, says Dr Prathit Kulkarni, assistant professor of medicine in infectious diseases at Baylor College of Medicine.

However, the neutralizing titers against the newer Omicron strains were approximately three-fold lower than BA.1, Moderna said in its recent press release.

Last week, the European Medicine Agency (EMA) started a rolling review of Moderna’s bivalent booster, alongside Pfizer/BioNTech’s potential variant-adapted Comirnaty vaccine, to prepare for vaccination campaigns this autumn. “Rolling reviews are an excellent way for the EMA to get a headstart in looking over clinical and other data in a real-time manner as it is published,” says Dr Rodney Rohde, chair and professor, Clinical Laboratory Science Program at Texas State University.

The US Food and Drug Administration (FDA) has not released a statement announcing rolling reviews yet, however, Moderna and Pfizer have stated their plans to submit data to both agencies. Reuters reported that FDA plans to hold a meeting next week to discuss the booster campaign for this autumn season, or fall as it is known elsewhere.

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On 22 June, following the most recent efficacy data on the Omicron subvariants, Stéphane Bancel, Chief Executive Officer of Moderna said “We will submit these data to regulators urgently and are preparing to supply our next generation bivalent booster starting in August, ahead of a potential rise in SARS-CoV-2 infections due to Omicron subvariants in the early fall.”

The FDA did not respond to a comment request from Pharmaceutical Technology about any review plans.

While the components of Moderna’s bivalent booster are clear, Pfizer/BioNTech have not announced which specific variants the new version of the Covid-19 mRNA vaccine will target. “I would be very surprised if they selected something other than the Omicron [variants] given where we are right now globally in the pandemic,” Kulkarni notes. The EMA stated that the agency will initially focus on the chemistry, manufacturing and controls (CMC) data for the component targeting Omicron subvariants.

Omicron subvariants dominate

According to Centers for Disease Control and Prevention (CDC) Covid Data Tracker, Omicron is the dominant SARS-CoV-2 strain, with BA.2.12.1 subvariant accounting for 56% of infections as recorded on 18th June. The prevalence of BA.2.12.1 has decreased by nearly 7% from the previous week while BA.4 and BA.5 have been emerging since the middle of May, and now account for 11.4% and 23.5% infections, respectively. Kulkarni predicts that the latest variants will dominate in the next few months.

As per Rohde, the spike protein in the Omicron variant has “wicked alterations” in its antigenicity, shows a very high transmission ability and immune escape from those early vaccine induced immune individuals. “Omicron-specific vaccines absolutely must have a place in the COVID-19 prevention toolbox.”

Rohde adds that there might be an ongoing need for other variant-specific vaccines or multidimensional vaccines for multiplex variants. Given SARS-CoV-2’s ability to mutate and change its genome, it is hard to say what will be the future variants of the virus.

“Theoretically, it is possible for a new variant to be more similar to previous strains than Omicron, but it is very difficult to predict,” Kulkarni says, while questioning the value of older variant-specific vaccines that both Moderna and Pfizer have in their pipeline.

More data needed for the rollout

Both experts say that adults, the elderly, and people who are the most at risk will receive the Omicron-specific vaccines first, as seen in the previous Covid-19 vaccine rollouts.

Rohde adds that he hopes to see a better global effort to distribute these vaccines to help with inequity as that continues to contribute to the emergence of new SARS-CoV-2 variants.

“Our number one priority with vaccination is to try preventing severe disease, hospitalization, and death, and if they can prevent infection, asymptomatic infection, and transmission, that is also an added benefit”, Kulkarni says.

It still unknown how long the immunity lasts from the original vaccines in conjunction with the rise of the new subvariants. Kulkarni expects to see data showing whether these Omicron-specific vaccines generate the right levels of neutralizing antibodies, safety and reactogenicity, as well as short- and long-term clinical profile, in scientific peer-reviewed publications and in formal reviews by the EMA and FDA.

“There are still many questions on the role of these vaccines and how [they] will get rolled out, but we will get more information and maybe by the end of summer, we will have a more solidified plan,” he notes.