Moderna says vaccine efficacy strong after six months, but booster likely
New data announced by Moderna is showing its mRNA COVID-19 vaccine remains significantly effective after six months. However, the company does note that a possible reduction in efficacy in the face of the new Delta variant indicates a likely need for third dose boosters later in 2021.
Moderna’s announcement reveals the final six-month follow-up data from its large 2020 Phase 3 trial. The impressive results show the vaccine has long-term durability with 93.2 percent efficacy against symptomatic COVID-19, 98.2 percent protection against severe COVID-19 and 100 percent protection against death.
“We are pleased that our COVID-19 vaccine is showing durable efficacy of 93% through six months, but recognize that the Delta variant is a significant new threat so we must remain vigilant,” says Moderna CEO Stéphane Bancel.
The efficacy data announced by Moderna was gathered prior to the emergence of the Delta variant. Additional data offered by the company shows neutralizing antibodies directed at new variants waning substantially after six months.
What this means for overall vaccine efficacy is still a source of great debate. Real-world data is beginning to indicate the Delta variant causes higher rates of symptomatic breakthrough infections in vaccinated individuals. But, these infections are still not likely to lead to severe disease, with vaccine protection from hospitalization and death still significant.
As recently expressed by Pfizer, these waning antibody levels are leading to suggestions of a third booster dose six to 12 months after initial vaccination. But the WHO is pushing back, saying there is little need for broad booster plans that would divert vaccine supplies away from low-income nations still waiting on deliveries of first doses.
Moderna’s announcement does offer early insights from ongoing Phase 2 trials testing COVID-19 vaccine boosters. A third booster, half the dose of its original vaccine, significantly increased neutralizing antibody levels above the peak seen in prior trials after a second dose. While the company is testing several new formulations designed to specifically target novel SARS-CoV-2 variants, the original vaccine formulation was still seen to be effective against Delta when administered as a third booster.
Data on an ongoing trial testing the original vaccine formulation in 12 to 17 year-olds was also revealed, indicating similar levels of efficacy and safety seen in adult trials. A Phase 2 trial testing the vaccine in children aged from six months to 11 years is still ongoing.
The company has also announced full enrollment for Phase 1 trialling of its next generation mRNA COVID-19 vaccine. This new version of the vaccine is designed to target different parts of the coronavirus spike protein in the hope of getting ahead of any new viral variants. This new vaccine formulation is also reportedly stable at warmer temperatures than its previous candidate, meaning it could be stored safely in refrigerators.