Pfizer says new Covid booster works better against omicron strains than old one in study

By Robert Langreth | Bloomberg

Pfizer Inc.’s bivalent vaccine bolstered protective antibodies against the dominant omicron strains substantially more than its original booster in people older than 55, according to a company study that suggests the new booster may provide an enhanced level of protection.

Pfizer and German vaccine partner BioNTech SE compared blood samples from 36 people older than 55 who had received the bivalent booster with those from a control group of people over 55 who had received a fourth dose of the original shot. One month later, antibody levels against the widespread BA.4 and BA.5 variants were four-fold higher in people who had received the bivalent shot when compared with those who had received another dose of the original vaccine, the companies said Friday in a statement.

Those findings contrast sharply with recent results from two independent labs at Columbia University and Harvard University. Both of those teams reported in October that bivalent boosters made by Pfizer and rival Moderna Inc. didn’t appear to provide much incremental benefit when compared with a fourth dose of the original vaccines, according to studies posted on the preprint server bioRxiv.org.

Pfizer’s own study, however, suggests that the bivalent shot “may induce a higher level of protection against the omicron BA.4 and BA.5 sublineages than the original vaccine,” the company said in its statement. The drugmaker has shared its results with the US Food and Drug Administration and said it plans to give them to regulators elsewhere soon.

Debate Implications

Pfizer didn’t release a direct comparison of how the bivalent booster fared in comparison with four doses of the original shot in adults younger than 55. But it did say that the bivalent shot raised antibodies against the BA.4 and BA.5 strains 9.5-fold in the 18- to 55-year-old age group compared to their pre-booster levels. In the over-55s, it raised antibody levels 13.2-fold. By comparison, a fourth shot of the original booster raised antibodies 2.9 times in people over 55.

A third academic study from Emory University posted this week was more in line with the Pfizer results, suggesting that the bivalent shot broadens immunity against omicron variants. However, a fourth study from researchers at the University of Texas Medical Branch in Galveston found that the bivalent shot, while generally stimulating more antibodies against omicron than the original vaccine, “does not produce robust neutralization” against the latest omicron strains, including the BQ.1.1. variant that’s rapidly taking hold in the US. Both studies were posted on bioRxiv.org.

It isn’t clear why various studies have produced what appear to be divergent results. All of them are small and have not yet been published in scientific journals.