Detailed study data for Moderna's experimental coronavirus vaccine were published in a major medical journal Tuesday, nearly two months after the Cambridge, Massachusetts-based biotech said a Phase 1 trial testing the shot had produced positive results.
The announcement in mid-May helped to raise confidence that the aggressive vaccine development timelines laid out by the U.S. government could possibly be met, lifting shares in Moderna and the broader stock market.
But the disclosure, made via a company statement, was criticized as an an example of "science by press release" and for benefiting Moderna without offering enough data to allow outside scientists to evaluate its claims.
The more complete results, published in the New England Journal of Medicine, back up Moderna's earlier statements, showing vaccination produced antibodies capable of neutralizing the SARS-CoV-2 virus in all of the study participants who were evaluated. Previously, Moderna had data on only the first eight adults tested for neutralizing antibodies.
The results so far are "promising" and support the vaccine's advancement, wrote Penny Heaton, the CEO of the Bill & Melinda Gates Medical Research Institute, in an editorial published alongside the study. They don't yet prove whether the vaccine can protect against coronavirus infection.
Three doses of Moderna's vaccine candidate were evaluated in the Phase 1 study, which was run by researchers at the National Institutes of Health and conducted at two sites in Seattle and Atlanta. As a first-in-human trial involving healthy volunteers, the primary goal was to assess whether the vaccine is safe.
After two months, most people experienced side effects that were generally mild or moderate in severity, commonly fatigue, chills, headache and muscle pain. Three adults given the highest dose experienced more severe fever-like symptoms, leading Moderna and the NIH to narrow their study to lower doses.
At the middle dose Moderna selected for late-stage testing, neutralizing antibody levels were, on average, two to four times higher than those measured in the blood of people with confirmed COVID-19. It's not yet clear what amount of coronavirus antibodies results in protection from infection. Still, scientists believe that looking at how the immune systems of recovered patients have responded could offer a guide.
Neutralizing antibodies only developed after a second "booster" shot that was given four weeks after the first, suggesting that any protection offered by Moderna's vaccine would take time to develop.
So-called "correlates of protection" are important. Knowing whether an interim, more easily obtainable measure like antibody levels eventually leads to immunity could help speed development of vaccines, and reassure regulators of the strength of early data.
But clear answers might not be readily available, particularly for a disease as complex as COVID-19.
"Half of the vaccines on the market don't have any clear immunological correlation of protection," said Paul Offit, director of the vaccine education center at Children's Hospital of Philadelphia, in an interview with BioPharma Dive. "We're so hungry for a vaccine we're trying to read the tea leaves."
While early data are all that's now available, Moderna has already moved its candidate into a mid-stage study that's enrolled all 600 planned participants. A Phase 3 trial, which will likely involve around 30,000 people and test whether the vaccine can prevent symptomatic COVID-19, is set to begin later this month.
The rapid advancement makes Moderna among the furthest along in a global effort to develop a coronavirus vaccine within 12 to 18 months, years faster than the norm. Some two dozen vaccines are now in clinical testing and preliminary information from studies of five other candidates, including one developed by Pfizer and BioNTech, have been made public.
Usually, clinical testing happens in sequence, a methodical process that allows researchers to carefully assess whether an experimental is safe and effective. Moderna, like others, has compressed that process immensely, beginning the next stage of development before obtaining full results from the step before.
Critically, Moderna doesn't yet have data on groups who are most at risk from coronavirus infection, such as older individuals or those who have existing health conditions. Additional volunteers, including elderly adults, have since been enrolled into the Phase 1 study.
Peoples' immune function declines with age, potentially posing the risk that the dose Moderna selected may not work as well for those who are older.
"Can they find the dose ... that provides the protection we need in older individuals and has a good safety profile?" asked Heaton in a separate interview with BioPharma Dive.
Tal Zaks, Moderna's chief medical officer, acknowledged in an interview that researchers still need to collect more data but expressed confidence the selected dose will work well for all groups.
"There's a balancing act there and I'm comfortable with the decision that we made," he said in an interview.
Moderna, working with federal scientists, was expected to begin its Phase 3 study earlier in July, but the start was delayed by several weeks, STAT reported. In a statement Tuesday, Moderna said the trial would start on July 27.
The breakneck pace at which Moderna and the NIH are advancing vaccine testing has led to some tensions between the two groups, according to Reuters, reportedly contributing to the delay.
In addition to working with Moderna on a Phase 3 trial, the U.S. government aims to begin over the next few months similarly large tests of vaccines developed by Johnson & Johnson, AstraZeneca and Novavax. All four companies are part of "Operation Warp Speed," an ambitious program that aims to quickly develop and make available multiple vaccines, potentially as early as the end of this year.
Wide-spread testing of vaccines will being getting underway as coronavirus outbreaks widen in many states in the U.S., which has reported about 60,000 new cases a day for the past week.
Jonathan Gardner and Ben Fidler contributed reporting.