Novavax on Wednesday said its vaccine targeting both Covid-19 and the flu triggered an immune response similar to its stand-alone shots against each virus, in an early indication that a combination vaccine targeting both viruses could prove effective though further study is necessary.
Chief Medical Officer Filip Dubovsky, during a call with reporters, said 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.
“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 combination,” Dubovsky said.
Participants in the phase one trial had a median age of 59 and all of them had previously received Covid vaccines. Novavax is presenting the data at the World Vaccine Congress in Washington, D.C., on Wednesday.
Novavax plans to move forward with a phase two trial this year to confirm the appropriate dosing levels, and launch a phase three trial on efficacy during the 2023 flu season at the earliest, Dubovsky said.
Public health experts expect Covid to become a seasonal respiratory virus similar to the flu that will likely require annual vaccination because immunity from the shots wanes over time. The vaccine makers are racing to develop combination shots targeting both viruses to make it easier for people to get protected when Covid and the flu are circulating simultaneously.
“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.”
Novavax, an early participant in the U.S. government’s 2020 race to develop Covid shots, does not currently have an authorized vaccine in the U.S. The company asked the Food and Drug Administration to authorize its Covid vaccine in January. Dubovsky told reporters on Wednesday that the FDA is still reviewing Novavax’s application.
Novavax’s Covid vaccine uses different technology than Pfizer‘s and Moderna‘s shots, which rely on messenger RNA to turn human cells into factories that produce copies of the virus spike protein, inducing an immune response that fights Covid. The spike is the part of the virus that latches onto and invades human cells.
Novavax’s shots, on the other hand, fully synthesize 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 vaccine also uses an adjuvant, an extract purified from the bark of a tree in South America, to induce a broader immune response. The adjuvant has been used in licensed vaccines against malaria and shingles. Novavax’s stand-alone Covid shots consist of 5 micrograms of the spike copy and 50 micrograms of the adjuvant.
Novavax uses the same technology for its stand-alone flu vaccine candidate, which targets four strains of the virus.
While the up to 25 microgram Covid formulation in the combination vaccine is higher than the stand-alone shot, Dubovsky said it’s well within the range of the other FDA-licensed Covid vaccines, which have dosing levels between 50 and 100 micrograms.
The 25 microgram formulation tested in the combination vaccine trial was well tolerated and safe, Dubovsky said. The most common side effects were injection site pain, fatigue and headaches, he said.