Pfizer’s New Omicron-Targeting Booster Produces Strong Immune Response

An early look at data from ongoing testing in people at least 18 years old found the booster generated higher levels of neutralizing antibodies against the two substrains compared with levels measured before the extra shot, the companies said.

Researchers also found the vaccine, called bivalent because it targets both the Omicron substrains as well as the original strain of the virus, was well-tolerated and worked safely.

“These early data suggest that our bivalent vaccine is anticipated to provide better protection against currently circulating variants than the original vaccine and potentially help to curb future surges in cases this winter,” Pfizer Chief Executive

Albert Bourla

said.

The findings provide the first results from testing of the retooled shots in people.

Antibodies provide the human immune system’s front-line defense, a rapid-fire force, on high-alert after vaccination, that spurs into action to neutralize the virus before it attacks cells.

Vaccines also mobilize other parts of the immune system but are more difficult to measure.

The U.S. Food and Drug Administrationcleared the new shots from Pfizer-BioNTech and from

Moderna Inc.

in late August, without waiting for results from the kinds of clinical trials conducted before earlier authorizations. The FDA clearance relied on results from testing experimental vaccines targeting the Omicron variant, animal studies and other data.

FDA officials and many vaccine experts said waiting for trial results wasn’t necessary because the changes simply updated proven shots, similar to the process used for annual flu shots, which are given without testing them in people.

More than 11 million Americans have received an updated booster shot, or 4.5% of the eligible population of those age 12 and older, according to the Centers for Disease Control and Prevention.

On Wednesday, the FDA authorized the shots for children as young as 5 years old.

In the study, researchers measured antibody responses by examining blood samples taken one week after subjects got the dose. They compared subjects who received the booster with those who got an additional shot of the original vaccine.

Among people 55 years and older, those who received a bivalent shot showed a stronger immune response against the substrains than those in the same age group who received a fourth dose of the original vaccine, the companies said.

The companies didn’t provide comparisons for younger people. The companies said they planned to provide more data in the future.

Write to Jared S. Hopkins at [email protected]