When Moderna revised the efficacy rate for its COVID-19 vaccine candidate, it wasn't an entirely unexpected development. The US-based pharmaceutical major announced on Monday said that its experimental coronavirus inoculation showed 94.1 per cent effectiveness, slightly lower than 94.5 per cent the company had claimed at the end of first interim analysis for the same jab. The underlying difference was the number of subjects in each analysis - the former had 196 patients, whereas the latter had only 95. Moderna's Phase 3 trial is being conducted with over 30,000 registrants.
Moderna said that its vaccine has been 100 per cent effective in 30 severe case of coronavirus infection. The company also claimed that its vaccine mRNA-1273 is generally well-tolerated and there are no serious safety concerns over the jab.
"Efficacy was consistent across age, race and ethnicity, and gender demographics. The 196 COVID-19 cases included 33 older adults (ages 65+) and 42 participants identifying as being from diverse communities (including 29 Hispanic or LatinX, 6 Black or African Americans, 4 Asian Americans and 3 multiracial participants)," Moderna said.
Unprecedented as it was, most vaccine manufacturers have claimed efficacy rates as high as over 90 per cent for their coronavirus jabs earlier this month. But those claims were based on very small trials of barely 100-odd cases. Such high level of initial efficacy is unprecedented. New vaccine rarely showcase efficacy over 90 per cent; most vaccines are usually rated in the range of40-60 per cent. Vaccine efficacies improve as millions are vaccinated over decades.
As for the under-development coronavirus vaccines in advanced stages, manufacturers had used extremely small sample groups, merely a fraction of the same for their entire Phase 3 clinical studies. Moderna's mRNA-1273 and BNT162b2 from Pfizer-BioNTech, the two vaccine candidates to have undergone primary efficacy analysis, had shown 196 and 170 patients respectively.
Meanwhile, the AstraZeneca-Oxford University had conducted an interim analysis on 131 COVID-19 patients, which showed varying levels of efficacy for different dosing regimens of its AZD1222 vaccine candidate. Russia's Gamaleya Center for Epidemiology and Microbiology had claimed 91.4 per cent efficacy after a recently conducted the second interim analysis for its Sputnik-V with only 39 participants.
Pfizer-BioNTech on November 9 stated said its COVID vaccine has attained 90 per cent efficacy. Two days later, Russia's Gamaleya Institute said its vaccine Sputnik V was 92 per cent effective. Moderna, which is also developing its vaccine on mRNA technology, said its vaccine had shown 94.5 per cent efficacy. Pfizer then released the findings for the final analysis of its vaccine candidate that suggested is 95 per cent efficacy rate. Now Moderna has said that its vaccine is 94.1 per cent effective, bringing down the efficacy rate slightly, but not by a lot.
Already under pressure to join the coveted league of frontrunners, Swedish pharmaceutical giant AstraZeneca, which has partnered with Oxford University, released its interim analysis data on November 23, saying their vaccine has shown 70 per cent efficacy against the COVID-19 virus. The company, however, said a lower dosage level of its vaccine emerged as more effective, generating about 90 per cent efficacy.
This raised eyebrows over the disparity in its clinical trial results. Now the company plans to conduct an extra global trial to straighten out the confusion from its current study.
Notably, Pfizer has approached regulators for emergency use authorisations for their respective vaccine candidates, while Moderna has its foot in the door. AstraZeneca is planning a similar course of action, to be put into play as soon as possible.
The regulators, usually feared for their zero-tolerance against shortfalls and harsh crackdowns, have been tight-lipped on the boisterous claims by vaccine developers.