Photo showing a patient having a flu vaccine injected into their arm by a healthcare professional (only the patient's shoulder and arm and the hands of the healthcare professional are visible)
Credit: Kmatta/Getty Images

German biotech CureVac has announced positive mid-Phase II data for its mRNA flu vaccine, which it is developing with big pharma GSK.

While the results showed better reactivity against more severe, pandemic-associated influenza A strains than currently available vaccines, the vaccine candidate was not as effective as current vaccines against less severe influenza B strains.

The company said it plans “further optimizations to enhance immune responses against influenza B strains” in another Phase II study.

CureVac’s flu vaccine uses its ‘second generation’ mRNA backbone and was tested in 480 healthy adults aged 18–65 years and 480 aged 65–85 years to assess safety and efficacy.

The company tested three different doses in each age group against approved comparator flu vaccines suitable for people of the same age. Immune responses in younger adults were compared to a standard dose of seasonal vaccine and immune responses in the older group to a high dose seasonal vaccine.

CureVac is not the only company developing an mRNA flu vaccine. Both Moderna and BioNTech, the latter in collaboration with Pfizer, have mRNA flu vaccine candidates and combined COVID and flu vaccine candidates at Phase III.

The interim results from CureVac’s flu vaccine, which was designed to protect against multiple strains of the virus, show better efficacy against influenza A strains of the virus, at all three doses, than conventional flu vaccines, but were less good at protecting against influenza B strains.

Notably, Moderna had a similar problem with its flu vaccine. When the company reported Phase III results last year, its vaccine was also more effective against influenza A than B strains.

It will be important for CureVac and other mRNA vaccine companies to solve the problem of inadequate protection against influenza B, as although the World Health Organization does update its flu vaccine recommendations regularly it currently recommends that annual flu vaccines should protect against the Yamagata and Victoria strains of influenza B.

The safety and tolerability of CureVac’s vaccine candidate in the trial was acceptable, with the majority of side effects being classified as mild or moderate.

“The Phase II interim data show that CureVac’s highly effective and flexible mRNA technology platform puts us on the right track to advance our joint seasonal influenza vaccine program,” said Myriam Mendila, Chief Development Officer of CureVac, in a press statement.

“Results regarding influenza A strains were strong. Immunogenicity for B strains was in line with our expectations also in view of other initial mRNA-based clinical flu development programs. We are confident that planned optimizations will improve performance against these historically challenging influenza strains.”

CureVac and GSK will now progress the flu vaccine further towards the clinic, but may struggle to keep up with rivals Moderna and BioNTech/Pfizer which are already at Phase III with several of their flu and combined COVID-19 and flu vaccine candidates.

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