German company CureVac on Wednesday delivered disappointing preliminary results from a clinical trial of its Covid-19 vaccine, tarnishing hopes of meeting the world’s great needs.
The study, which included 40,000 volunteers in Latin America and Europe, estimated that CureVac’s mRNA vaccine was only 47 percent effective, one of the lowest ever reported by any Covid vaccine manufacturer. The study will continue as researchers monitor volunteers for new cases of Covid, with a final analysis expected in two to three weeks.
“We’re going into full swing for the last reading,” said Franz-Werner Haas, CEO of CureVac, in an interview. “We are still planning to submit the permit.”
CureVac plans to first apply to the European Medicines Agency for approval. The European Union reached an agreement last year to purchase 405 million doses of the vaccine if the agency approves it.
However, independent experts said it would be difficult for CureVac to recover. Natalie Dean, a biostatistician at the University of Florida, said the vaccine’s effectiveness could improve somewhat by the end of the study. However, since most of the data are already available, the vaccine is unlikely to offer high protection. “It’s not going to change dramatically,” she said.
And with such a low rate of efficacy – far less than the roughly 95 percent of competing mRNA vaccines from Pfizer-BioNTech and Moderna – the results aren’t a good sign that CureVac’s vaccines will be adopted.
“It’s pretty devastating for them,” said Jacob Kirkegaard, a vaccine supply expert at the Peterson Institute for International Economics, a Washington think tank.
The news was disappointing to experts who had hoped the company could provide vaccines to low- and middle-income countries that don’t have nearly enough. CureVac had several advantages over the other mRNA vaccines, such as the month-long shelf life in the refrigerator. In addition, CureVac’s vaccine uses fewer mRNA molecules per injection compared to its competitors, reducing its cost.
The study results published on Wednesday were based on data from 135 volunteers suffering from Covid. An independent panel compared the number of people who had received a placebo with those who had received the vaccine. Although the vaccine appeared to offer some protection, the statistical difference between the two groups was not great, giving an effectiveness rate of 47 percent.
In comparison, annual flu vaccinations can be 40 to 60 percent effective. Both the World Health Organization and the Food and Drug Administration set a threshold of 50 percent effectiveness for considering Covid vaccines for emergency approval. If CureVac ended up staying at 47 percent, it wouldn’t meet that standard.
The results surprised the scientists. CureVac’s recordings have shown promising results in animal studies and early clinical studies.
“This is a bit of a head scratch,” said Dr. Dean.
Dr. Haas blamed the disappointing results on the high number of virus variants in the countries where the vaccine was tested. Of 124 of the Covid-19 cases that the company’s scientists have genetically sequenced, only one was caused by the original version of the coronavirus.
More than half of the cases were caused by variants that have been shown to be more transmissible or can make vaccines less effective. CureVac volunteers have also been infected by variants that have yet to be carefully investigated. Lambda, which has dominated Peru for the past few weeks, made up 21 percent of the samples.
Dr. Haas said the results should serve as a wake-up call to the threat that new variants can pose to vaccine effectiveness. “It’s a new Covid reality, that’s for sure,” he said.
Moderna and Pfizer-BioNTech were tested last year before variants emerged, which could partly explain their much higher rates of effectiveness. However, studies have shown that their effectiveness in practice falls only moderately in view of variants.
Dr. Kirkegaard predicted that it would be challenging for CureVac to compete with others Covid vaccine under development, manufactured by Novavax. Novavax reported Monday that its non-frozen vaccine was 90 percent effective in a study in the United States and Mexico.
“I suspect that it will be difficult for them to really get a significant market for developing countries,” said Dr. Kirkegaard.
