Myocarditis, pericarditis
The Novavax vaccine is already authorized in other countries, including Canada. Novavax in February announced that it had begun shipping its first doses of the vaccine to European Union member states. The vaccine can be moved through existing vaccine supply and cold chain channels instead of requiring complex new delivery procedures.
That could prove an advantage in time, said FDA panelist Michael Nelson, MD, PhD, of the University of Virginia, Charlottesville.
“Who knows even with supply chain challenges down the road, it will be nice to have options going forward,” Dr. Nelson said.
As with other COVID-19 vaccines, clinicians and researchers are still working to understand the potential risk for inflammation of heart muscle and nearby tissue with vaccination. Most patients with myocarditis or pericarditis who sought medical care for these conditions responded well to medicine and rest and felt better quickly, the CDC says on its website. They usually return to their normal daily activities after their symptoms improve.
At the June 7 meeting, Dr. Nelson said there may be cases of myocarditis that go undetected.
“Our signals are those who get admitted to the emergency room and the hospital,” he said. “I’m quite convinced that there are others who are experiencing cardiac events of lesser severity that are worthy of being studied, both from mechanistic and outcomes standpoints. So we have a lot of work to do.”
In looking at results for an initial pool of 40,000 people who received the Novavax vaccine, there were five reported cases of myocarditis or pericarditis developing within 20 days of people getting the shot, the FDA staff said in its presentation on safety.
In a briefing document released ahead of the advisory committee meeting, the FDA staff flagged this number of cases in a relatively small database as a concern, noting it “could be higher than reported during postauthorization use of mRNA COVID-19 vaccines (for which no cases were identified in preauthorization evaluation).”
Novavax officials took a somewhat unusual step of responding in public. The Gaithersburg, Md.–based company on June 3 issued a statement saying researchers had come to “expect to see natural background events of myocarditis in any sufficiently large database, and that young males are at higher risk.”
The data from the company’s placebo-controlled studies show that, overall, in its clinical development program, the rate of myocarditis was balanced between the vaccine and placebo arms (0.007% and 0.005%), Novavax said.
At the June 7 meeting, FDA panelists including Dr. Nelson, and Paul A. Offit, MD, of Children’s Hospital of Philadelphia, urged continued study to try to determine whether and how the vaccines could trigger myocarditis. Investments made now in pursuing these questions related to COVID-19 shots may pay off later, Dr. Offit said.
“We can use that knowledge to make safer vaccines for a disease that is going to be with us for decades, if not longer,” he said.
A version of this article first appeared on Medscape.com.