One of the first COVID-19 vaccines to begin trials in human subjects seems to be safe and effective, according to interim data released on May 18. While this is definitely good news, experts are still saying that the absolute earliest a vaccine could be widely available would be the end of this year.
This vaccine candidate, known as mRNA-1273, prompted an immune response in study participants, announced its manufacturer, Moderna, Inc., in a press release this morning. It was also found to be well-tolerated.
The human trials for the vaccine candidate began on March 16 in four people, though ultimately, 45 people were included in the study. About a month later, subjects received a second dose.
Two weeks after receiving a second dose, participants’ levels of binding antibodies — immune substances that bind to the virus — met or exceeded the levels seen in the blood serum of people who had recovered from COVID-19. The same appears to be true of levels of neutralizing antibody, which bind to the virus and block infection; but the data for this type of antibody was only available for eight of the study participants.
“The important element here is that in general, neutralization correlates with total binding antibodies once you’re above a certain threshold. So the relevance of these results, for us, is not just the direct confirmation that in these first eight subjects, indeed, we see neutralizing activity. But they really allow us to extrapolate what we expect to be achieving in all 45 subjects,” said Tal Zaks, MD, PhD, Moderna’s chief medical officer, during a conference call. He added that preclinical animal trials showed that the vaccine prevented SARS-CoV-2 viral replication in animals’ lungs. “These data today take off the table the risk of not being immunogenic, or the risk of the antibody type being wrong — no, it works, and you see the demonstration of neutralizing activity,” Dr. Zaks said.
The interim data also showed that the vaccine was generally safe and well-tolerated. Three participants experience flu-like symptoms after receiving a second vaccination at a 250 microgram dose, the highest included in the phase one trial. These symptoms were resolved within a day. But because the early data shows that the lower doses (25 micrograms and 100 micrograms) were so effective, the researchers are dropping the highest dose from its next trials. Plus, as Dr. Zaks told The New York Times, “The lower the dose, the more vaccine we’ll be able to make.”
At the lowest dose, just one person experienced a reaction: redness around the injection site.
“The only side effect I experienced was soreness at the site of injection the day after the two doses,” Jennifer Haller, a participant in this human trial and one of the first people to receive the mRNA-1273 shot, confirmed in an email to Refinery29. “But both times it was less uncomfortable than flu shots I’ve had in the past, so that was a welcome surprise.”
Haller said she just found out about the interim data this morning from the news. “They announced last week that the trial was approved for stage two, and that was a good sign, but to hear this morning that binding antibodies were detected even in the lowest dose group (my group), that’s so exciting!” She said she’s not assuming these early results mean she’s immune, and she still plans on taking measures such as social distancing and wearing a face mask. But she’s hopeful, and heartened by the success. “Science is real,” she said.
Now, Dr. Zaks and the other researchers working on this vaccine are turning their sights to the next phases of trials. The phase two study, which is expected to begin soon, will test different doses of mRNA-1273, and a placebo, on 600 participants aged 18 and over. The third phase will involve thousands of participants, and ideally include people who are at risk because of factors including their ages, pre-existing conditions, or occupations, Dr. Saks said.
If all goes well, Dr. Zaks told The New York Times, a coronavirus vaccine could be available by the end of this year or early 2021.
COVID-19 has been declared a global pandemic. Go to the CDC website for the latest information on symptoms, prevention, and other resources.
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