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A third dose of Moderna Inc.’s Covid-19 vaccine increased antibody levels against the omicron variant, results the company described as reassuring while it works on a shot tailored to the new strain.
A 50 microgram booster dose produced a 37-fold increase in neutralizing antibodies, the company said in a statement Monday. That is the same dose as the currently authorized Moderna booster, which is half the dose used for primary immunization. The company also tested a 100 microgram dose, which increased antibody levels 83-fold compared with the primary two-dose course.
The results add to a growing body of evidence that three shots will be needed to neutralize the fast-spreading omicron. Pfizer Inc. and BioNTech SE said earlier this month that a third shot of their vaccine restored protection to a level similar to the initial two-dose regimen against the original virus.
The data are “reassuring,” Moderna Chief Executive Officer Stephane Bancel said in a statement. “To respond to this highly transmissible variant, Moderna will continue to rapidly advance an omicron-specific booster candidate into clinical testing in case it becomes necessary in the future.”
However, analysts cautioned that it will take time to determine just how long the shot is able to provide substantial immunity.
“The actual fold increase is only valuable if it’s compared with other vaccines,” said Sam Fazeli, a Bloomberg Intelligence analyst. “These levels should increase protection against infection but the key question is how long do they last.”
Even with the lower dose, “the magnitude of boosting we are seeing here is quite reassuring,” Moderna president Stephen Hoge said on a conference call with analysts Monday. “We think we are comfortably above what for other variants of concern was a correlate of breakthrough risk.”
On the conference call with analysts, Hoge said that the company could have six-month followup data showing how long the protection with the original booster holds up in the early part of 2022. He declined to provide more exact timing for the durability data.
The Moderna data are based on lab tests using blood sera from 20 booster recipients with each dose, with antibody levels measured on day 29 post-boost, the company said. Moderna said it plans to submit the results for online publication.
Moderna is testing different booster candidates against a range of variants in mid and late-stage trials. The biotech said it plans to start testing its omicron-specific vaccine in humans early next year. It has also been testing the safety and tolerability of the higher 100 microgram booster dose.
The higher dose level was generally well tolerated, with adverse events at a similar frequency to those experienced after the primary two-dose course. There were slightly more frequent side effects from the 100 microgram third dose than the 50 microgram booster, the company said.
While the 100 microgram booster dose led to significantly higher neutralizing antibodies than the standard 50 microgram booster dose, Moderna officials on the call said they had no plans to formally ask regulators for authorization of the higher dose as a booster.
On the call, Hoge noted that a 100 microgram third dose is already authorized in the U.S. for people who are immune compromised, and he said the 100 microgram dose uses the same vials. That makes the logistics easy if public-health officials choose to recommend a higher booster dose for certain groups at higher risk, he noted.
Hoge said the company was moving ahead with its program to develop an omicron specific booster. It’s possible that an omicron-specific booster could provide longer-lasting protection than the existing booster shot, even if it doesn’t generate higher antibody levels over the short term.
Long-term, the continued emergence of more and more variants increases the likelihood that regular seasonal boosters for the Covid-19 vaccine are going to be needed, just like they are needed for influenza, Moderna executives said on the call. The company is planning for a seasonal booster market where people at high risk of severe disease would continue to get periodic Covid boosters.
“We believe that we are going to be living with this virus, its strains and variants, forever,” Hoge said.
Créditos: Comité científico Covid