CureVac vaccine shows 47-percent efficacy

Prevention Problem

German vaccine maker CureVac said Wednesday that a preliminary analysis of late-stage testing of its coronavirus shot show a comparatively low effectiveness in protecting people against COVID-19. CureVac is looking for a new mRNA molecule that will be more effective against a wide variety of variants, but CureVac’s stock dropped by 45 percent in Germany, erasing nearly $8 billion from the company’s value.

The clinical trial involving its mRNA candidate showed the vaccine was about 47-percent effective in preventing symptomatic coronavirus illness. The late-stage trial involved 40,000 participants in 10 countries across Latin America and Europe.

While the results appear to be a significant setback for CureVac’s efforts to develop a coronavirus vaccine, the company said that the trial is ongoing and it still plans to file for approval in the EU. Still, the EU’s threshold for efficacy to receive an emergency authorization is 50 percent. The World Health Organization has said vaccines with an efficacy above 50 percent are worth using, but many already approved vaccines have a far higher rate.

CureVac blamed the 13 known COVID variants now in circulation, relating that more than half of the first 147 volunteers who fell ill had contracted one of the “variants of concern.” Additionally, the results cloud the picture of mRNA vaccines being a sure shot against the coronavirus. Both the Pfizer/BioNTech and Moderna vaccines are much less effective against different variants.

While not all the data from its trial of 40,000 participants in Latin America and Europe have been analyzed yet, the company said interim results show the vaccine has an efficacy of 47 percent against COVID-19 disease of any severity. Results did not meet what the company said were its “prespecified statistical success criteria.”

According to CureVac’s chief executive, Franz-Werner Haas, “While we were hoping for a stronger interim outcome, we recognize that demonstrating high efficacy in this unprecedented broad diversity of variants is challenging, but the overall vaccine efficacy may change. The study is continuing to the final analysis and the totality of the data will be assessed for the most appropriate regulatory pathway.”

Outside experts cautioned against comparing CureVac’s data directly with other shots already authorized for use. Deborah Fuller, a professor of microbiology and vaccine specialist at the University of Washington School of Medicine, said that CureVac was dealing with “quite a different environment” than some of its rivals who had tested their shots when the original variant was still dominant. CureVac’s trials took place in 10 different countries, so “the more countries you’re testing in, the more variants you have to test against.”

Additionally, the mRNA technology used in the CureVac shot is slightly different from that used in the BioNTech-Pfizer and Moderna vaccines, according to Mark Slifka, a professor of microbiology and immunology at Oregon Health and Science University. CureVac uses unmodified mRNA, which could cause a different immune response in the body that affects the efficacy, he said. “It could be the variants, it could be the type of mRNA, or it could be a combination of all of the above,” he added.

Haas concluded that the large number of variants CureVac encountered in its trial — with only a single case of COVID-19 attributable to the original variant — “underlines the importance of developing next-generation vaccines as new virus variants continue to emerge.”