Study: Moderna immunity wanes 6 months in but still protective

BOSTON — Wonderful. Awesome. Fantastic. Those are the adjectives Emory University researcher Mehul Suthar used to describe the immunity levels seen just after the second dose of Moderna’s COVID-19 vaccine.

But Suthar and colleagues at Emory’s Vaccine Center found that stunning immunity dulled after six months but not to such an extent that the vaccine was ineffective. In fact, Suthar estimated that in three age groups studied – 18-to-55, 56-to-70 and 71-and-older – neutralizing antibodies should linger for one to two years.

That is, neutralizing antibodies to the virus strain the vaccine was designed to handle, which is the only one that was circulating at the time of its development: the one from Wuhan.

“Now, there are so many more variants,” Suthar said. “That’s really the next set of questions. How well does this durability hold up in the face of these variants?”

Against the British or Kent variant – B.1.1.7 – Suthar is betting Moderna’s vaccine and others will do quite well. But other variants carry a mutation known as E484K or 484, which has also been found in a limited number of samples of B.1.1.7.

“The 484 mutation has been identified by several groups, including ours, that it seems to escape antibody responses,” Suthar said. “Other groups are finding that mutations within what’s called the N-terminal domain of that spike protein also encode for escape antibodies.”

Suthar said the question becomes whether normal-over-time reductions in antibody levels with current COVID-19 vaccines will leave hosts open to reinfection by variants with ‘escape antibody’ mutations.

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“Does that mean we need a booster to help us get back to the awesome fantastic level? It’s unclear,” he said.

Also unclear – and under study – is whether a booster of the same vaccine formulation will do the trick against variants or whether the vaccine would need readjustment to thwart a specific mutation.

As these issues are studied, COVID-19 is having the equivalent of a global field day.

“Roughly 75% of the vaccines that have been manufactured are only going to 10 countries in the entire world,” said Dr. Ingrid Katz of Brigham and Women’s Hospital, who recently co-wrote a piece in the New England Journal of Medicine calling for a global vaccination effort.

Dr. Katz estimated at the current rate of vaccination, it could take four years to immunize the rest of the world.

“And I think that is a real problem when you think about the number of variants that can continue to come up,” she said. “Even in this small window of time, over the course of this past year, we’ve seen multiple variants now emerge. So it’s only going to be continuing to escalate.”

And doesn’t Suthar know it. He pointed to the emergence of numerous new strains in Brazil, Mexico and the recent importation of a ‘double mutant’ from India.

“Three days ago, four days ago it was found in the San Francisco Bay area,” he said. “You can see how mutants in one area, one geographical location of the world, can spread and seed themselves in another geographic location.”

Suthar said mask-wearing, to mitigate the spread and transmission of COVID-19, is key to slowing down the emergence of new variants.

“Because of the rates of transmission and spread of this virus, this has just allowed this virus to test mutation space,” he said, “To figure out what works best for that virus to infect, replicate, transmit.”

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