Moderna: new clinical data on its Covid-19 vaccine 

New analysis suggests that the Moderna Covid-19 vaccine is highly effective against circulating variants of concern, including in a vaccine effectiveness study conducted in partnership with Kaiser Permanente Southern California (KPSC) and in a separate recent publication by the US Centers for Disease Control and Prevention (CDC).  

Additionally, the company shared a new analysis of follow-up through one year in the Phase III COVE study suggesting a lower risk of breakthrough infection in participants vaccinated more recently (median eight months after first dose) compared to participants vaccinated last year (median 13 months after first dose).  

“It is promising to see clinical and real-world evidence adding to the growing body of data on the effectiveness of the Moderna Covid-19 vaccine,” said Stéphane Bancel, Chief Executive Officer of Moderna. “The increased risk of breakthrough infections in COVE study participants who were vaccinated last year compared to more recently illustrates the impact of waning immunity and supports the need for a booster to maintain high levels of protection. We hope these findings are helpful as health authorities and regulators continue to assess strategies for ending this pandemic.” 

In a prospective cohort study at KPSC, an analysis of 352,878 recipients of two doses of mRNA-1273 matched to 352,878 unvaccinated individuals found a vaccine effectiveness of 87% (99.3% CI: 85-90%) against Covid-19 diagnosis and 96% (99.3% CI: 91-98%) against Covid-19 hospitalisation1. The study was conducted during the emergence of the Delta variant, which was identified in 47% of cases in fully vaccinated individuals. These data have been posted to a preprint server and submitted for peer review. 

Recent data published by the US CDC2 examined vaccine efficacy across nine states based on 32,867 medical encounters including 14,636 hospitalisations between June and August 2021, during the time when the Delta variant became predominant in the United States. In the analysis, the Moderna Covid-19 vaccine efficacy against Covid-19 urgent care or emergency visit was 92% (95% CI: 89-93%) and against hospitalisation was 95% (95% CI: 92-97%) at a median of 96 and 106 days respectively after vaccination. Across all age groups, vaccine efficacy was reported to be significantly higher among Moderna vaccine recipients than other Covid-19 vaccines. 

The goal of the Phase III COVE study between July 1, 2021 and August 27 is to quantify the impact of waning immunity in the face of the Delta surge in the US. The analysis compared participants initially randomised to mRNA-1273 (vaccinated from July-October 2020; n=14,746; median follow-up of 13 months since first dose) against participants initially randomised to placebo who were crossed over and vaccinated following Emergency Use Authorization (vaccinated from December 2020-March 2021; n=11,431; median follow-up of 8 months since first dose). 

In the analysis, 88 breakthrough cases of Covid-19 occurred in the more recently vaccinated group (49.0 cases per 1000 person-years) compared to 162 cases in the group vaccinated last year (77.1 cases per 1000 person-years). The reduction in incidence rates for participants vaccinated more recently compared to participants vaccinated last year was 36% (95% CI: 17-52%). A Cox proportional hazards model showed similar results after adjusting for age and risk factors for severe Covid-19. Fortunately, only 19 severe cases were observed. While not significant, there was a numerical trend towards a lower rate of severe cases in the group vaccinated more recently (3.3 per 1000 person-years) compared to the group vaccinated last year (6.2 per 1000 person-years). 

The increased risk of breakthrough in this analysis quantifies the impact of waning immunity in the COVE study between the median follow-up time of 8 months and 13 months since first dose. The company believes this adds to evidence of potential benefit of a booster dose of mRNA-1273. 

 Image credit: Mufid Majnun

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