Final analysis of US-funded Moderna Covid vaccine trial shows 98% efficacy against severe disease
A final look at the results of the placebo-controlled Moderna trial in the New England Journal of Medicine, published Thursday afternoon, shows how the vaccine continues to prevent Covid-19 and severe cases after more than five months following the second shot.
Of the more than 30,000 enrolled in the trial that ultimately led to the vaccine’s EUA, only two people in the vaccine group got a severe form of the disease, compared to 106 in the placebo group — leading to an efficacy of 98%.
As the company prepares to submit data to the FDA on a booster shot, it’ll likely have a difficult time, as Pfizer has, showing that the two-shot combo has waned in efficacy enough for the general population to immediately receive a third dose.
Efficacy in preventing overall Covid-19 illness, the primary endpoint of the Moderna trial, was 93%, with 55 confirmed cases in the vaccine group and 744 in the placebo group.
“Vaccine efficacy was consistently high in subgroups, including participants 65 years of age or older and 75 years of age or older, those with coexisting conditions, those belonging to various racial and ethnic groups, and those with various categories of occupational risk exposures,” Harvard’s Lindsey Robert Baden and Baylor’s Hana El Sahly, the article’s lead co-authors, wrote.
The article is the final analysis of the vaccine’s blinded phase of the trial, which was funded by both the US government’s BARDA and Tony Fauci’s NIAID. BARDA has spent billions of dollars developing and manufacturing the vaccine, now known commercially as Spikevax. And Moderna is likely to haul in at least $20 billion from it just this year, based on the expected manufacture of between 800 million and 1 billion doses.
While previous analyses of this trial and others have shown strong vaccine efficacy against symptomatic or overall Covid-19 infections, the Moderna trial also looked specifically at asymptomatic cases too, which could be key with the rise of the Delta variant.
In terms of preventing asymptomatic infection 14 days after the second injection, the results show the efficacy of the vaccine was 63% (95% CI, 56.6 to 68.5), with 214 asymptomatic cases in the Spikevax group and 498 in the placebo group.
The CDC says that with Delta, it is continuing to assess data on whether fully vaccinated people with asymptomatic breakthrough infections can transmit the virus. Some studies have attributed the rise of Delta at least in part due to stealth asymptomatic infections.
As for safety, the final results of Moderna’s trial offer up similarly encouraging data showing some injection-related side effects, but less than 0.1% of patients in both vaccine and placebo groups discontinued participation in the trial because of adverse events after either injection.
Overall, 0.6% of placebo recipients and 0.4% of vaccine recipients had adverse events that resulted in their not receiving the second dose, and adverse events that were considered to be related to the injections were reported by about 9% of placebo recipients and 14% of vaccine recipients during the observation period of the study and were generally similar to those reported previously regardless of age.
A total of 32 deaths occurred by completion of the trial, the authors noted, with 16 deaths each in the placebo and vaccine groups, although “no deaths were considered to be related to injections of placebo or vaccine.” Four of the deaths were attributed to Covid-19, with three coming from the placebo group and one in the vaccine group, although that one individual in the vaccine group only received one dose of Spikevax.