More COVID-19 Updates: Monovalent vs Bivalent Boosters’ Efficacy

Volume 23, Issue 4

It seems that as we progress through the winter, the deluge of data regarding the updated bivalent COVID-19 boosters’ effectiveness continues. I was hoping to talk about some recently published data on the efficacy of various diuretic regimens in patients with acutely decompensated heart failure, but I will have to table that discussion, as we have more vaccine data to discuss this week.

Point 1: Data for Antigenic Response Continues to Evolve

A few weeks ago, I looked at various data evaluating the effect of the bivalent boosters formulated against BA.5 vs the traditional monovalent boosters. Against BA.5, there was no appreciable difference between the two vaccines, but against some newer strains like XBB and BQ.1.1, the bivalent boosters performed moderately better than the monovalent boosters.

In a new study published this week in The New England Journal of Medicine, the authors evaluated the efficacy of various vaccine boosters against the contemporary variants of concern. In this new analysis, the BA.4.6, BA.2.75.2, BQ.1.1, and XBB.1 strains were involved.

After monovalent booster dose, geometric mean titers increased at 1 month postvaccination by:

• 3.0 against the ancestral strain;
• 2.9 against BA.4 and BA.5;
• 2.3 against BA.4.6;
• 2.1 against BA.2.75.2;
• 1.8 against BQ.1.1; and
• 1.5 against XBB.1.

On the other hand, the bivalent vaccine induced neutralizing geometric mean factor increases of 5.8, 13.0, 11.1, 6.7, 8.7, and 4.8, for each respective strain.

Interestingly, those with a prior history of COVID-19 developed higher neutralizing titers than those without a prior infection.

Point 2: Finally, Some Real-World Data

All this talk about neutralizing antibody titers is interesting, but the real meat and potatoes of this discussion is whether the new boosters are more effective than their predecessors in protecting patients from the new variants.

In another new study, 2 cohorts of patients who received either a mono- or bivalent booster were followed postvaccination so researchers could evaluate rates of severe infection (hospitalization or death due to COVID-19 infection with variants BA.4.6, BA.5, BQ.1, or BQ.1.1). These authors found vaccine effectiveness against severe infection was 24.9% (95% CI, 1.4 to 42.8) for the monovalent booster and 61.8% (95% CI, 48.2 to 71.8) for the bivalent booster. The bivalent booster was therefore associated with an increase in vaccine effectiveness of 36.9 percentage points (95% CI, 12.6 to 64.3).

These results were consistent across various age groups and were not influenced by prior infection or type of original vaccine received.

Taken together, these new studies build on prior data demonstrating the new bivalent vaccines provide superior protection from novel variants.