People looking for a booster dose of a COVID-19 vaccine probably don’t have to worry about the brand – according to a new large-scale study, many vaccine combinations appear to provide strong protection.
In a comparison of seven different vaccine brands, British researchers found that most of them elicited a strong immune response, with mRNA injections from Moderna and Pfizer-BioNTech obtaining the highest responses. The study was posted on thursday in The Lancet.
“These data are welcomed by policy makers,” said Merryn Voysey, a statistician at the University of Oxford who was not involved in the study. “The most significant message we are left with is that there are a large number of excellent third-dose booster options.”
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–It’s too early for researchers to say how well the various booster vaccines will work against the new omicron variant, which has mutations that could allow it to bypass some of the antibodies produced by existing COVID-19 vaccines. Some researchers suspect that people would need a very high level of antibodies to protect themselves against it.
The 2,878 study volunteers initially received two injections of the AstraZeneca or Pfizer vaccines. (Both vaccines are licensed in the UK; injections from Pfizer, Moderna, and Johnson & Johnson have been licensed in the US.)
The researchers then tested seven different vaccines as boosters: Together with AstraZeneca and Pfizer, they used three brands that have been licensed in several countries: Johnson & Johnson, Moderna, and Novavax. They also tested two vaccines that have not been licensed anywhere: a CureVac mRNA vaccine, and a Valneva vaccine made from inactivated coronaviruses. Finally, some of the volunteers received a meningitis vaccine as a control.
After four weeks, the researchers took blood samples from the volunteers and measured their antibody levels. They also looked for immune cells, known as T lymphocytes, that specifically attack other cells infected by the coronavirus.
Antibody and T-cell levels increased in people who received a booster vaccine for COVID-19 compared to those who received the meningitis vaccine. However, the range was quite wide. People who received the Valneva booster after a Pfizer vaccine only saw a 30 percent increase over the control group. But the Moderna reinforcement produced an increase of at least 1,000 percent.
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–The new study also found that the boosters increased the T cells that recognize the coronavirus. Antibodies can be good at killing the coronavirus early in the infection, when the virus is colonizing the nose. But deep in the airways, T cells can provide a second line of defense.
Volunteers were not followed up in the trial to see how well the booster vaccines actually prevented infection or disease. However, in recent months researchers have shown that measuring antibody levels can be a pretty good way to predict the effectiveness of a vaccine.
Most of the boosters used in the study raised antibodies to a level that would equal at least 90 percent protection against infection. And the mRNA vaccines from Pfizer and Moderna produced much higher antibody levels than the other vaccines.
“I would say that regardless of what was obtained the first time, having an mRNA boost is probably a good idea,” said Eleanor Riley, an immunologist at the University of Edinburgh who was not involved in the new study.
However, other scientists claimed that most of the other vaccines in the study performed well enough that people were comfortable using them as well.
“If your country or region of the world only has one of the vaccines that we have shown can boost, then there will be no problem using it as a booster and it will be safe to do so,” said Saul Faust, an infectious disease expert at the University of Southampton and co-author. of the study. “Not everything is mRNA.”
John Moore, a virologist at Weill Cornell Medicine in New York, who was not involved in the study, said people shouldn’t make too much of the modest differences between most vaccines.
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–“I don’t consider it a beauty pageant, in the sense of which one is slightly superior to another,” he said. “We can’t afford to be too picky about this.”
Moore said the new study could give public health officials the confidence to turn to different vaccines for boosters, depending on which one is more convenient. Novavax and Johnson & Johnson, for example, make vaccines that can be stored in refrigerators, while mRNA vaccines have to be kept frozen.
An unavoidable flaw of the new study is that the researchers did not measure the reinforcements against the new omicron variant. Discovered last month, omicron has raised great concern among researchers due to its numerous mutations. A booster that is 90 percent effective against the parent strain could do poorly against omicron.
It is not known how bad. The omicron experiments have not started because scientists must first figure out how to grow the variant in the laboratory. Faust and his colleagues have already sent blood samples from the trial volunteers to British government laboratories, where researchers will see how well their omicron-boosted immune cells and antibodies work. “I think we’ll start to see those results in a few weeks,” Faust said.
If the boosters don’t work well against the variant, vaccine developers will have to make new formulations, said Stanley Plotkin, a vaccine expert and professor emeritus at the University of Pennsylvania. The mRNA vaccines could be quickly adapted to target omicron mutations, he added, or researchers could try a more difficult approach: a universal vaccine against any coronavirus.
“Assuming that omicron eludes the antibodies against the original virus and the current variants, then we have to assume a different philosophy,” he said.
Carl Zimmer is the author of the Matter column. He has published 14 books, including Life’s Edge: The Search For What It Means To Be Alive. @carlzimmer
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