Moderna 2-strain booster shows strong subvariant antibody response

Moderna vaccine being drawn into syringe
Moderna vaccine being drawn into syringe

Anthony Quintano / Flickr cc

Moderna today reported that that the bivalent (two-strain) mRNA vaccine it developed against Omicron showed a strong neutralizing antibody response against the Omicron BA.4 and BA.5 subvariants and that it will seek regulatory approval in the coming weeks.

Moderna's bivalent vaccine contains its original vaccine plus a strain that targets Omicron and its subvariants.

The announcement comes amid rising BA.4 and BA.5 levels worldwide, which are fueling new spikes in cases, the World Health Organization (WHO) said today in its latest update.

Projected August availability for booster

News of a strong performance against BA.4 and BA.5 comes just 2 weeks after the company announced that its bivalent COVID booster candidate, given as a 50-microgram dose, prompted a higher response against the Omicron variant than the current version of its vaccine.

In today's announcement, Moderna said the bivalent booster upped neutralizing antibodies 5.4-fold against BA.4 and BA.5 above baseline in all participants, regardless of prior infections, with a 6.3-fold increase in a group of seronegative participants—those showing evidence of past infection.

One month after receiving the bivalent booster, neutralizing geometric mean titers (GMTs) were against BA.4 and BA.5 were 941 in all participants and 727 in the seronegative group. For comparison, earlier studies of the booster induced a neutralizing GMT of 629 against BA.1 and 828 against the Delta variant. A higher GMT indicates a more robust immune response.

Stephane Bancel, Moderna's chief executive officer, said the company is encouraged by the booster's performance against BA.4 and BA.5, which are an emerging health threat. "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," he said.

In the United States, overall COVID-19 activity shows signs of a slow rise, though it's difficult to precisely gauge, due to decreased testing and the growing use of at-home tests. Activity levels are brisk, especially in areas where BA.4 and BA.5 are most prevalent, especially the south central states. The Texas Department of State Health Services said today that the positivity rate is over 23% in that state, and cases, hospitalizations, and deaths continue to rise.

Slow global decline continues, but BA.4, BA.5 expand

In its latest weekly update today, the WHO said cases last week dropped 4% compared to the previous week, with deaths down 16%. However, two regions—Southeast Asian and the Eastern Mediterranean—saw modest increases, while the European region registered a small increase.

The WHO included the caveat that case patterns should be interpreted with caution because of decreased testing.

In Southeast and South Asia, countries reporting sharp rises last week include Bangladesh, Maldives, Indonesia, and India. In the Eastern Mediterranean region, several countries reported spikes, including Iraq, the United Arab Emirates, Oman, and Bahrain. Europe's slight rise was led by increases in Germany, France, and Italy, as well as some Eastern European countries.

The WHO said BA.5 and BA.4, which share a mutation associated with higher transmissibility, are, when taken together, increasing in prevalence—from 32% the previous week to 34% for the most recent week.

BA.5 accounts for 25% of sequenced samples, up from 16% the week before, and BA.4 is at 9%, down from 16% the previous week. So far the two subvariants have been detected in 62 and 58 countries, respectively.

Levels of BA.2.12.1, another Omicron variant, which was first identified in New York, are declining.

"The rise in prevalence of BA.4 and BA.5 has coincided with a rise in cases in several WHO regions. In some countries, the rise in cases has also led to a surge in hospitalizations and [intensive care unit] admissions," the WHO said. It added, however, that the current evidence doesn't show changes in severity.

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