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.
The first confirmed omicron infection in the United States was reported Wednesday in San Francisco, in a traveler who returned to California from South Africa on Nov. 22. The individual had been fully vaccinated — but had not received a booster — and showed mild symptoms that were said to be improving.
Omicron carries more than 50 genetic mutations, more than 30 of them on the virus’ spike, a protein on its surface. Vaccines train the body’s immune defenses to target and attack these spikes.
Not all experts are lining up in support of booster shots.
The push for extra doses is predicated on the idea that antibodies are the central aspect of immunity, a false perspective that overlooks the importance of other parts of the immune system in preventing severe illness and death, said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and an adviser to the Food and Drug Administration.
He said he would be more worried if vaccinated people infected with the omicron variant were hospitalized in droves. But limited evidence to date suggests that the vaccines still prevent severe illness, he said.
If necessary, multiple booster doses — first with the current vaccines, then with Omicron-specific versions — would need to be exquisitely timed, because stimulating immunity too frequently can backfire, Moore said. Certain immune cells may stop responding to the vaccines.
“This is where it all gets complicated — certainly, nobody should be sitting on dogma here,” he said. “We’re reacting in a low-information environment where the consequences are potentially quite serious.”
