Data hints omicron milder, better at evading vaccines
JOHANNESBURG — The omicron variant is offering more hints about what it may have in store as it spreads around the globe: A highly transmissible virus that may cause less severe disease, and one that can be slowed — but not stopped — by today’s vaccines.
An analysis Tuesday of data from South Africa, where the new variant is driving a surge in infections, suggests the Pfizer vaccine offers less defense against infection from omicron and reduced, but still good, protection from hospitalization.
The findings are preliminary and have not been peer-reviewed but they line up with other early data about omicron’s behavior, including that it seems to be more easily spread from person to person.
Still, some experts cautioned that it’s too soon to draw conclusions.
When omicron reaches broader populations, more useful information will emerge, said Dr. David Dowdy, an infectious disease epidemiologist at Johns Hopkins Bloomberg School of Public Health.
“To date, omicron has disproportionately infected young adults — people who probably have more social contacts and are more likely to attend large gatherings,” Dowdy said. Young adults may be more likely to be sick without knowing it, have more intense exposures and experience milder disease, he said.
“At the end of the day, our society needs to learn how to wait, rather than either panicking or dismissing early findings,” Dowdy said.
U.S. health officials estimate that a small, but growing proportion of new COVID-19
infections are due to omicron.
Two weeks ago, omicron accounted for less than 0.5 percent of the coronaviruses that were genetically sequenced in the U.S. That rose to about 3 percent last week, the Centers for Disease Control and Prevention reported Tuesday.
But it varies from place to place, and is as high as 13 percent in the New York/ New Jersey area, according to the agency.
In Britain, omicron cases are doubling every two to three days. Health officials say the variant will replace delta as the dominant coronavirus strain within days.
In the new South Africa findings, people who received two doses of the Pfizer-biontech vaccine appeared to have just 33 percent protection against infection, compared with those who were unvaccinated, during the country’s current omicron-fueled surge, but 70 percent protection against hospitalization. The analysis was conducted by Discovery Health, South Africa’s largest private health insurer, and the South African Medical Research Council.
The study did not look at
booster shots.
The Pfizer vaccine’s 70 percent protection against hospital admission during the omicron surge compares with a 93 percent protection level seen in South Africa’s delta-driven wave, according to the new analysis.
That’s a big drop, said Dr. Eric Topol, head of the Scripps Research Translational Institute.
“What we don’t know yet is whether the booster will restore that back to greater than 90 percent and for how long,” Topol said.
In the weeks since the variant was detected, South Africa has experienced rapid spread of the virus. The seven-day rolling average of daily new cases in the country rose over the past two weeks from 8.07 new cases per 100,000 people on Nov. 29 to 34.37 new cases per 100,000 people on Dec. 13, according to Johns Hopkins University. The death rate hasn’t increased during that same period.
Experts now say that omicron accounts for more than 90 percent of all new infections in South Africa, according to Discovery Health chief executive Dr. Ryan Noach.