German company CureVac announced the final results of its late-stage vaccine study on Wednesday, confirming earlier data showing that its vaccination is far less protective than other vaccines.

Overall, the CureVac vaccine was only 48 percent effective against Covid-19. Moderna and Pfizer-BioNTech vaccines, which use the same mRNA technology as CureVac’s, have shown efficacy rates of around 95 percent in clinical trials.

In younger subjects, the CureVac vaccine proved to be slightly better: in the 18- to 60-year-olds, the effectiveness increased to 53 percent. In this group, the researchers also found that the vaccine offered 100 percent protection against hospitalization and death.

40,000 people took part in the company’s study in Europe and Latin America. By the end of the study, 288 volunteers had been infected with Covid-19.

CureVac struggled with 15 different variants of the coronavirus. Genetic testing showed that only 3 percent of the cases were caused by the original version of the coronavirus. It is possible that some of the variants were able to bypass the immunity produced by the CureVac vaccine. (No variants were widely available in 2020 when Moderna and Pfizer-BioNTech conducted their trials.)

However, vaccine experts have also questioned whether part of the CureVac problem is related to the design of the vaccine itself. The exact recipe CureVac used to make its vaccine may have weakened its effectiveness.

The European Medicines Agency launched an ongoing review of CureVac’s vaccine in February, and the company announced that it would continue filing with these dates. The vaccine “will make an important contribution to coping with the Covid 19 pandemic and the spread of the dynamic variant,” said Franz-Werner Haas, Managing Director of CureVac, in the announcement.