Novavax has developed a new vaccine that targets both COVID-19 and the flu and triggers an immune response similar to its stand-alone shots against each virus, the company said.

According to Chief Medical Officer Filip Dubovsky, the company's early phase clinical trial found that up to 25 micrograms of the COVID formulation, combined with up to 35 micrograms of the flu formulation, triggered a promising level of protective antibodies, CNBC reported.

"What we demonstrated in this study is we were able to get the immune responses really comparable to what the individual vaccines did prior to the combination," Dubovsky was quoted as saying. Unlike mRNA vaccines, Novavax's shots fully synthesise the virus spike outside the human body. The genetic code for the spike is put into a baculovirus that infects insect cells, which then produce copies of the spike that are purified and extracted.

The spike copy, which can't replicate or cause COVID, is injected into people to induce an immune response against the virus, the report said. The vaccine also uses an adjuvant, also used in vaccines against malaria and shingles, which contains an extract purified from the bark of a tree in South America, to induce a broader immune response.

Novavax's stand-alone COVID shots consist of 5 micrograms of the spike copy and 50 micrograms of the adjuvant. The same technology has been used for its stand-alone flu vaccine candidate, which targets four strains of the virus. In the phase one trial for its new vaccine, participants had a median age of 59 and all of them had previously received COVID vaccines. Novavax presented the data at the World Vaccine Congress in Washington, DC, on April 20.

To confirm the findings, Novavax aims to launch a phase two trial this year, and a phase three trial on efficacy during the 2023 flu season at the earliest, Dubovsky said. Even as public health experts expect COVID to become a seasonal respiratory virus similar to the flu, vaccine makers are racing to develop combination shots targeting both viruses.

"Combination vaccines are an attractive public health intervention," Dubovsky said. "You are hitting two life-threatening diseases in one medical contact, giving a single vaccination." While Novavax does not currently have an authorised COVID vaccine in the US, it had in January asked the Food and Drug Administration to authorise its COVID vaccine. However, the FDA is still reviewing Novavax's application, Dubovsky said.