Many public health experts were opposed to a boosters-for-all approach. The new variant is changing some minds.

As recently as last week, many public health experts were fiercely opposed to the Biden administration’s campaign to roll out booster shots of the coronavirus vaccines to all American adults. There was little scientific evidence to support extra doses for most people, the researchers said.

The Omicron variant has changed all that.

Scientists do not yet know with any certainty whether the virus is easier to spread or less vulnerable to the body’s immune response. But with dozens of new mutations, the variant seems likely to evade the protection from vaccines to some significant degree.

Booster shots clearly raise antibody levels, strengthening the body’s defenses against infection, and may help offset whatever advantages Omicron has gained through evolution.

Many of the experts who were opposed to boosters now believe that the shots may offer the best defense against the new variant. The extra doses may slow the spread, at least, buying time for vaccine makers to develop an Omicron-specific formulation, if needed.

“Based on what we know about the potential for immune evasion, I would err on the side of giving the booster,” said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center who had opposed the Biden administration’s boosters-for-all push.

The administration isn’t waiting for scientific consensus. Alarmed by the preliminary reports about Omicron, officials at the Centers for Disease Control and Prevention said on Monday that all American adults should receive booster shots.  ...