Novavax announced Tuesday that its potential vaccine to prevent Covid-19 generated a promising immune response in an early stage clinical trial, but the biotech company's stock fell briefly on concerns about its safety.
The phase one trial included 131 healthy participants between the ages 18 and 59 at two sites in Australia. Novavax said 106 participants received one of four dose levels of the potential vaccine, named NVX-CoV2373, with or without an adjuvant, which is an ingredient designed to enhance the immune response. The remaining 25 patients received a placebo.
Participants received two doses of the potential vaccine via intramuscular injection approximately 21 days apart, the company said.
The vaccine produced neutralizing antibodies, which researchers believe are necessary to build immunity to the virus, and killer T-cells, the company said. Additionally, the neutralizing antibodies that were produced were higher than those seen in people who have recovered from Covid-19, Novavax said. The immune response was also stronger for those who had the adjuvant, the company said.
Novavax said the vaccine was well tolerated with no serious adverse events reported. Most patients reported tenderness and pain at the injection after the first dose, with some patients also reporting headaches, fatigue or muscle aches. Only one participant in the trial experienced a mild fever after a second dose, the company said. Earlier media reports and analysts cited eight possible hospitalizations related to the study, but the company said no patients were hospitalized.
Shares of the company were down as much as 32% in after-hours trading before later recovering and rising more than 7%.
Public health officials say there is no returning to "normal" until there is a vaccine.
Novavax is among several companies racing to develop a vaccine to fight the virus, which has infected more than 18 million people worldwide and killed at least 694,715 as of Tuesday, according to data compiled by Johns Hopkins University. There are more than 150 vaccines under development globally, according to the World Health Organization, with at least 25 already in human trials.
The announcement comes less than two weeks after drug companies Pfizer and Moderna both announced they began their late-stage trials for potential coronavirus vaccines. Those trials will include about 30,000 participants.
"The Phase 1 data demonstrate that NVX-CoV2373 with our Matrix-M adjuvant is a well‑tolerated COVID-19 vaccine with a robust immunogenicity profile," Gregory Glenn, president of research and development at Novavax, said in a statement Tuesday.
While Novavax's data appears promising, scientists warn that questions remain about how the human body responds once it's been infected with the virus. The answers, they say, may have important implications for vaccine development, including how quickly it can be deployed to the public.
One question among scientists is whether antibodies produced in response to Covid-19 offer protection against getting infected again.
Scientists expect that antibodies provide some degree of protection against getting Covid-19, but they can't say that definitively yet since the virus was first discovered just seven months ago.
Novavax's vaccine contains synthesized pieces of the surface protein the coronavirus uses to infect humans.
Last month, the U.S. government, as part of the Trump administration's Operation Warp Speed initiative, announced it would pay Novavax $1.6 billion to develop and manufacture the potential vaccine, with the aim of delivering 100 million doses by the beginning of next year.
The money will also cover the cost of running a late-stage trial, which could begin as early as October.
The company has said it would begin a phase two trial in multiple countries if the early stage trial was successful.