A flurry of new lab studies indicate that vaccines, and especially booster shots, may protect against the worst outcomes of the rapidly spreading Omicron coronavirus variant. However, the highly mutated virus will still cause many breakthrough infections in vaccinated people and those infected with older versions of the virus, according to the study.
At a World Health Organization meeting on Wednesday, scientists reported on several studies suggesting that T cells in vaccinated people may provide a strong defense against the variant, which could help prevent serious illness, hospitalization and death.
Also on Wednesday, Dr. Anthony S. Fauci, President Biden’s chief medical adviser on the coronavirus response, provides preliminary data from his institute’s analysis of the Moderna vaccine. While two shots produced a negligible antibody response to Omicron in the lab, protection skyrocketed after a third dose, he said.
Other researchers at the WHO meeting presented similar results, showing that booster shots of Moderna or Pfizer-BioNTech mRNA vaccines reduced the antibodies to levels deemed high enough to provide strong protection against infection.
While the study is based on preliminary observations of cells in the lab, it’s nevertheless a welcome change from a deluge of disturbing new data on Omicron. Over the past week, it has become increasingly clear that Omicron can deftly evade antibodies, part of the body’s first line of defense, which likely explains why infections with the variant have exploded in many countries. But antibodies aren’t the only key players in a person’s immune response to the virus. T cells have their own role.
“The good news is that T-cell responses are largely conserved on Omicron,” said Wendy Burgers of the University of Cape Town during a presentation of new research she and her colleagues conducted in recent days.
Omicron infections are more common in two groups of people who carry antibodies: those who have been vaccinated, and those who have not been vaccinated but have recovered from a previous infection with the coronavirus.
This week, scientists in South Africa reported that two doses of the Pfizer vaccine were 33 percent effective against an Omicron infection, up from about 80 percent during what Dr. Fauci called “the pre-Omicron era.” The study found that two doses of the Pfizer vaccine provided 70 percent protection against severe hospitalization and death, up from about 95 percent before Omicron was detected.
At Wednesday’s WHO meeting, scientist after scientist presented similar lab findings showing that vaccine-induced antibodies performed much worse against Omicron than against other variants.
But boosters seem to provide enough additional antibodies to reduce these infections. dr. Fauci described experiments at the National Institutes of Health in which scientists took blood serum from people who had received two doses of the Moderna vaccine, as well as from others who had received a third dose. The researchers then mixed the serum with viruses designed to carry Omicron’s surface proteins.
These “pseudoviruses” evaded many of the antibodies from people given two doses of Moderna, but the boosters produced such high levels of antibodies that the viruses were blocked from entering cells.
“So the message remains clear: If you’re not vaccinated, get vaccinated, and especially in the Omicron arena, when you’re fully vaccinated, you get a booster shot,” said Dr. Fauci.
dr. Fauci’s admonition comes as Biden officials brace for a potential wave of Omicron infections that could overwhelm the health care system. The Centers for Disease Control and Protection recently warned that the percentage of coronavirus cases in the United States, caused by the Omicron variant, had risen sharply and could predict a significant increase in infections next month. The Delta variant remains by far the dominant version in the United States.
In anticipation of that surge, the government is trying to encourage all eligible Americans — those 16 and older who received their second vaccine dose at least six months ago — to get their booster shots. About 27 percent of fully vaccinated Americans have also had booster shots, according to the CDC
Many countries are rushing boosters to their populations, but Omicron is spreading so fast that it may outstrip even the best efforts.
“The expected transmission rates, if confirmed, won’t give us much time for interventions,” Phil Krause, a former vaccine regulator at the Food and Drug Administration, said at the WHO meeting.
That prospect has led many scientists to hope that T cells will serve as an effective backup when antibodies fail. If these immune cells can fight off Omicron, they can prevent many infections from turning into serious disease.
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After a cell is infected with the coronavirus, T cells can learn to recognize fragments of viral proteins that land on the outer surface of the cell. The T cells then kill the infected cell, or alert the immune system to launch a stronger attack against the virus.
dr. Alessandro Sette, an immunologist at the La Jolla Institute for Immunology, and Andrew Redd of the National Institutes of Health reported that despite Omicron’s many mutations, most protein fragments recognized by T cells are identical to those of other variants.
Those findings suggest that T cells trained by vaccines or previous infections will respond aggressively to Omicron, rather than watch. “It appears that the T-cell response is largely preserved,” said Dr. Sette.
dr. Burgers and her colleagues tested that possibility by collecting T cells from 16 people vaccinated with two doses of the Pfizer-BioNTech vaccine and exposing those T cells to protein fragments of the Omicron variant. The scientists found that the T cells’ response to the variant was about 70 percent as potent as their response to the original form of the virus.
A number of scientists at the meeting warned that this data comes from studying cells in a lab known as in vitro experiments. It will take a few more weeks to study infections in humans before it becomes clear how well T cells prevent serious disease.
“We do not yet know what these in vitro findings actually mean for the severity of the disease,” says Nora Gerhards, virologist at Wageningen University in the Netherlands. “And that’s what matters. Because ultimately we want to prevent a collapse of the health care systems in our countries.”
