Modern data gives hope for better Covid-19 booster shots
Modern data gives hope for better Covid-19 booster shots

Modern data gives hope for better Covid-19 booster shots

NNew data from Moderna gives hope that booster shots against Covid-19 can at least be somewhat more effective than they already are. But the data also points to how difficult it can be to determine exactly which Covid shots to give as annual boosters.

On Tuesday, Moderna released data that tested a booster shot that is bivalent, meaning it contains equal amounts of vaccine from two different virus strains. This booster, currently known by the code number mRNA-1273.211, contains equal amounts of mRNA of ancestral SARS-CoV-2

and peak proteins from the Beta variant of SARS-CoV-2, which originally appeared in South Africa. It does not contain vaccine specifically targeted at the Delta or Omicron variants that caused the recent waves of Covid-19.


But the bivalent booster generated levels of antibodies that blocked all newer variants – Beta, Delta and Omicron – better than the existing Moderna Covid vaccine. “We believe these results validate our bivalent strategy, which we announced and began pursuing in February 2021,” said Modern’s CEO Stephane Bancel in a statement.

For each variant, neutralizing antibody levels for the 50 microgram dose of the booster were approximately twice the existing Moderna booster dose.


Despite the encouraging data, a pre-printed next to the company’s press release – that is, a paper that has not yet been peer-reviewed by external scientists – highlights the limitations of this study.

“The study was not designed and randomized to compare different booster candidates or dose levels head-to-head, and the evaluation of booster candidates was sequential and open,” the authors write. Neither were neutral targets for neutralizing antibodies generated in the laboratory at the same time.

This means that it is impossible to say whether the antibody boost provided by the mRNA-1273.211 vaccine prevents infections or serious illness better than the existing booster.

At a hearing of a Food and Drug Administration Advisory Panel Earlier this month, experts were concerned about exactly how governments should make decisions on the composition of annual boosters. And they were adamant that governments, not pharmaceutical companies, should determine the tribal composition of the shots that the World Health Organization makes for flu shots. But these data are a reminder that these decisions can be difficult. What would experts do when faced with booster images with several different compositions? Will adding new strains work the same way for different types of vaccines? There are a large number of open questions.

There’s also the biggest problem with annual flu shots: People do not get them. Even with the current Covid boosters, this has been true. Data presented to the FDA panel said 217 million Americans have been vaccinated against Covid. But only 90 million people have received a booster dose. How many show up for a new booster next year?

Moderna does not proceed with this vaccine based on these data. Instead, it is conducting another study of its booster shot based on the Omicron strain – it is called mRNA-1273,214, with results so far in the second quarter. That study seems to randomize volunteers to receive either the new booster or the original, then should provide clearer data. Moderna said in its release that its goal is to “inform the selection of its candidate for the Northern Hemisphere fall 2022 booster.”

Moderna did not return a request for comment on the design of their Omicron booster survey.

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