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A potential Covid-19 vaccine from the biotech company Novavax showed a promising immune response in a small, early trial, but not without a high rate of mostly mild side effects.

The results, published Tuesday, are the latest encouraging sign in the global effort to develop a vaccine for the novel coronavirus, which has killed nearly 700,000 people around the world. But the Novavax data, much like results recently published by Moderna and AstraZeneca, are too preliminary to draw any conclusions about how well the vaccine might protect against Covid-19, experts said.


“It’s a small number of people in each arm, and the study wasn’t designed to demonstrate efficacy, which are the standard caveats for a Phase 1 trial,” said Edward Belongia, an epidemiologist and vaccine researcher at the Marshfield Clinic Research Institute in Wisconsin. “Having said that, it looks very promising — at least as promising if not more so than the other vaccines we’ve looked at.”

The data were published on a preprint server, meaning they have not yet been peer-reviewed.

Novavax enrolled about 130 healthy volunteers in its trial and gave them either a placebo or one of four escalating doses of its vaccine. Everyone who received the vaccine developed neutralizing antibodies against SARS-CoV-2, which may help prevent infection.


The best responses came from volunteers who received two injections of Novavax’s vaccine three weeks apart, plus an adjuvant meant to boost its effects. After 35 days, those participants had neutralizing antibody levels that, on average, were roughly four times higher than what was seen in a group of 32 patients who had recovered from the disease.

About 80% of those volunteers had side effects at the site of injection, including pain and tenderness. More than 60% had other side effects, mostly headaches, muscle pain, and fatigue. Most reactions were mild or moderate, but eight patients had side effects that were graded severe; Novavax said none required hospitalization. All of the reactions resolved after a few days, and none was life-threatening.

The study, conducted in Australia, recruited a roughly even number of men and women between the ages of 18 and 59. Volunteers were about 79% white, 15% Hispanic, 13% Asian, 6% Indigenous, and 2% Black. The median age was 31.

Whether the vaccine’s demonstrated effect on neutralizing antibodies will protect people from Covid-19 remains unclear. Scientists are still mapping out the underlying mechanisms that drive immunity to SARS-CoV-2.

It’s also impossible to directly compare Novavax’s product, NVX-CoV2373, against other vaccines in development, said Kathryn Edwards, scientific director of the Vanderbilt Vaccine Research Program in Nashville, Tenn. Injections from Moderna, AstraZeneca, CanSino, and the partnership of Pfizer and BioNTech all elicited neutralizing antibodies in early trials, but each study used different methods to detect immune responses, meaning they can’t be judged on a head-to-head basis until there’s data on actual SARS-CoV-2 infection rates.

Overall, the Novavax trial is “another encouraging study that looks like the vaccine may be a potential winner, but efficacy and safety studies need to continue,” Edwards said.

Moderna, AstraZeneca, and Pfizer are all recruiting more than 30,000 volunteers each for placebo-controlled Phase 3 trials meant to determine whether their vaccines can prevent Covid-19. Novavax plans to begin a similar study of its own in the fall, joined by Johnson & Johnson, Sanofi, and others.

Novavax’s vaccine is among a handful being funded by Operation Warp Speed, a U.S. effort to develop treatments and vaccines for the novel coronavirus by the end of this year. The company is in line to receive $1.6 billion in federal funding, which will support its development efforts and pay for 100 million doses of NVX-CoV2373 if it proves to be safe and effective. The company is also receiving up to $388 million from the Coalition for Epidemic Preparedness Innovations, a nonprofit funded in part by the Bill and Melinda Gates Foundation.

NVX-CoV2373 is engineered to mimic a key protein found on the surface of SARS-CoV-2, simulating viral infection to compel the body to produce antibodies against Covid-19. Novavax, which has no approved products, has spent nearly three decades and $1.5 billion trying to develop vaccines with its technology.

An earlier version of this story incorrectly stated that trial volunteers who experienced severe reactions were hospitalized.

  • There were 8 patients had severe side effects this need to be investigated how do you know NAVX is telling the truth and other news reported that investigation to find the truth Low level company like NAVX never bough single vaccines for 33 years ?? Investors will get hurt by lying cheating executives that can not tell the truth ?? Investigation needed

    • Absolutely incorrect. There were no severe reactions. That was a complete mistake (which has been admitted) by Damian. This was irresponsible reporting with mistaken understanding of the science – not any misreporting by NVAX.

  • It’s not a money making thing – it’s a responsible journalism thing. What Damian published was dead wrong. That’s the issue. It’s impact on markets is obviously unfortunate- but that’s not the main issue. Damian needs to be more responsible when reporting information as true.

  • So Damian – are you going to apologize for getting it completely wrong. Fortunately I held my shares – but your comments cost many a bunch of money. I would be reporting this to your malpractice insurance- your reporting was negligent. Please try harder in the future to get it right. That was a remarkably irresponsible article which had a significant impact on the market.

  • If there were really 8 hospitalizations, the FDA would have unblinded the trial and stopped it immediately! Would have never reached this point. Insane that you didn’t think that through before publishing it.

    • The story behind 8 patients had severe side effects and hospitalized there should be no severe side effects, safety and effective , lying , cheating executives to profit going to 2& 3 trial than it did not sorry and couple thousands shares be sold and investors will be hurt and patients my die in next trial this is outrageous and investigation should start to find the truth and only the truth ??

    • Hank – Damian got it 100% wrong and has admitted it. He misinterpreted the information because of his lack of expertise. There were no hospitalizations or severe reactions. Damian made a huge mistake which he has admitted. It was negligence on his part. Again, he has admitted it.

    • “Unsolicited adverse events were collected through 28 days after Dose 2. There were no severe (Grade 3) unsolicited adverse events, and the vast majority of adverse events were mild and deemed not related to vaccination. No serious adverse events (SAEs) were reported and safety follow-up continues.”

      So either the above is wrong or Damian is wrong – and Damian has already admitted he was wrong.

  • I can tell you all this is the real deal. Once in a lifetime. Now is the time to get in. It’s like buying Tesla when it was 100$ a share or ground floor of Amazon or Apple. Now think folks. There are 6+ Billion souls on the planet. 6 billion. Does that ring a bell. If a company has the no kidding best vaccine it’s off to the moon past Mars on the way out …. up. If you invested a few thousand in Amazon Tesla or Apple at the beginning what would that be worth now. Better jump on now before the train goes all the way out the station. Everything I have read from scientific community say that Novavax is out in front of everyone else. So when and they will have best Phase 3 Trial results the Government will give them boo coo $ to produce and distribute it. And it will be licensed out to other companies and every country except China … not sure about Iran n North Korea because they would give it to China to steal

  • The fake news regarding the 8 patients cost me several grand, sold some of my position at the 30% drop, the reporter Damian Garde should be fired and your company should be sued, going forward you should have two reporters agree on stories that have the potential to move stock prices.

  • How many mom and pop retail investors will wake up Friday to the great news only to find out their stop losses sold all their shares durning the 1/2 hour this article (prior to correction) created a free fall. They lost 20-30 percent and then the stock recovered and passed today’s closing price. Leaving mom and pop out of the success loop. Investigators will hold you accountable!

  • Where are you getting “but eight patients had side effects that were graded severe; Novavax said none required hospitalization.”? Novavax press release reads “There were no severe (Grade 3) unsolicited adverse events” and “No serious adverse events (SAEs) were reported”. If you don’t know how to read a press release and you don’t even know what “Grade 3” means (as you admitted on Twitter) you shouldn’t have a job reporting on biotech.

    • I agree – story is still inaccurate. I guess if journalists were paid like immunologists this kind of “mistake” likely wouldn’t happen. I use word “mistake” based on ignorance and complete lack of awareness of impact of said mistake on full display in twitter account.

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