People looking for a booster shot of a Covid-19 vaccine probably needn’t worry about which brand it is: Many combinations of shots are likely to provide strong protection, according to a major new study.
In a comparison of seven different vaccine brands, British researchers found that most of them elicited a strong immune response, with the mRNA shots from Moderna and Pfizer-BioNTech eliciting the largest responses. The research was published in The Lancet on Thursday.
“This is welcome data for policymakers,” said Merryn Voysey, a statistician at the University of Oxford who was not involved in the study. “The main message here is that there are a myriad of excellent stimulant options for third doses.”
It’s too early for researchers to say much about how well different vaccine boosters will work against the new Omicron variant, which has mutations that allow it to evade some of the antibodies produced by existing Covid-19 vaccines. Some researchers suspect that people need very high levels of antibodies to protect themselves against it.
All 2,878 study volunteers initially received two injections of either the AstraZeneca or Pfizer vaccine. (Both vaccines are approved in Britain; injections from Pfizer, Moderna, and Johnson & Johnson are approved in the United States.)
The researchers then tested seven different vaccines as boosters: Together with AstraZeneca and Pfizer, they tried three brands that are authorized in different countries: Johnson & Johnson, Moderna and Novavax. They also tried two injections that have not been approved anywhere: an mRNA vaccine from CureVac and a vaccine from Valneva made from inactivated coronaviruses. Finally, some volunteers received a meningitis vaccine as a control.
After four weeks, the researchers collected blood samples from the volunteers and measured their antibody levels. They also looked for immune cells, known as T cells, that specifically attack other cells infected with the coronavirus.
Antibodies and T-cell levels increased in people who received a Covid-19 booster shot compared to those who received the meningitis vaccine. However, the offer was quite large. People who received the Valneva booster after a Pfizer vaccine saw only a 30 percent increase over the control group. But a Moderna booster drove an increase of at least 1,000 percent.
The new study also found that boosters increase T cells that recognize the coronavirus. Antibodies can be good for knocking out the coronavirus early in an infection, when the virus colonizes the nose. But deep in the airways, T cells can provide a second line of defense.
The trial did not follow the volunteers to see how well the booster shots actually prevented infection or disease. But in recent months, researchers have shown that measuring antibody levels can be a pretty good way to predict a vaccine’s effectiveness.
Most boosters used in the study increased the antibodies to levels that would be the equivalent of 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’d say whatever you got the first time, having an mRNA booster is probably a good idea,” said Eleanor Riley, an immunologist at the University of Edinburgh who was not involved in the new study.
Still, other scientists said most of the other vaccines in the study performed well enough that people should feel comfortable getting them as well.
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“If your country or region of the world only has one of the vaccines that we’ve shown can boost, that’s fine to use as a booster and safe to do it,” said Saul Faust, an expert on the subject. field of infectious diseases at the university. of Southampton and a co-author of the study. “It’s not just about mRNA.”
John Moore, a virologist at Weill Cornell Medicine in New York who was not involved in the study, said people shouldn’t take advantage of the modest differences between most vaccines.
“I don’t think of it as a beauty pageant, in the sense that one is slightly higher than the other,” he said. “We can’t afford to be too precious about this.”
dr. Moore said the new study could give public health officials the confidence to use different booster vaccines, depending on what was most convenient. For example, Novavax and Johnson & Johnson make vaccines that can be stored in refrigerators, while mRNA vaccines must be stored frozen.
An inevitable shortcoming of the new research was that the researchers did not measure the boosters against the new Omicron variant. Discovered only last month, Omicron has raised serious concerns among researchers because of its many mutations. A booster that is 90 percent effective against the original species may do worse against Omicron.
How much worse is unknown. Experiments with Omicron have not yet started because scientists first need to figure out how to grow the variant in the lab. dr. Faust and his colleagues have already sent blood samples from the trial volunteers to UK government labs, where researchers will see how well their boosted antibodies and immune cells work against Omicron. “I think we’ll start to see those results in a few weeks,” said Dr. Faust.
If boosters don’t work well against the variant, vaccine developers will have to make new shots, said Dr. Stanley Plotkin, a vaccine expert and professor emeritus at the University of Pennsylvania. The mRNA vaccines could be quickly adapted to address Omicron’s mutations, he added, or researchers could try a more challenging approach: a universal vaccine against any coronavirus.
“Assuming that Omicron escapes antibodies to the original virus and current variants, then we must have a different philosophy,” he said.