University Hospitals in Cleveland will begin a clinical trial of a booster shot of the Pfizer COVID-19 vaccine this week.
About 10,000 people nationwide will participate in trials testing whether an extra dose of the vaccine significantly strengthens immune response, said Dr. Robert Salata, chair of UH’s department of medicine.
Pfizer announced last week it will seek authorization in August for a booster shot of its two-dose COVID-19 vaccine, but there is uncertainty among health experts about whether people need it, Salata said.
“There’s no definitive answer right now as to whether they’re even necessary,” Salata said. “They basically said, this is a wait and see.”
After Pfizer’s announcement, the U.S. Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) said in a joint statement that Americans who are fully vaccinated do not need a booster yet.
“FDA, CDC, and [The National Institutes of Health] are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary,” the statement reads.
Pfizer officials said they were developing the shot a study in after Israel showed the vaccine’s efficacy has diminished, Salata said.
The trials are also in response to the delta variant, the more contagious strain of the virus that now accounts for half of new cases in the United States, Salata said. In one subset of new cases in a UH lab, the presence of delta increased from 7 percent two weeks ago to 42 percent last week, he said.
While the Pfizer vaccine appears to protect well against the delta variant, Salata said, researchers want to see if an additional dose will strengthen protection. Down the line, researchers also may develop new vaccines specifically targeted at delta, he added.
Dr. Daniel Culver, chair of pulmonary medicine at Cleveland Clinic, agrees that more data is needed to determine recommendations for boosters. An extra dose may be useful for vulnerable populations – such as cancer patients and older people – but not everyone, he said.
“I think there’s just not enough evidence to support a widespread rush to getting boosters,” Culver said.
Health experts expected vaccine antibodies to wane eventually, Culver said, but the vaccine also helps immune systems make the memory cells that extend protection for longer time periods.
“It’s really what’s going on in the bone marrow, where the memory cells are sitting, which are shown to be lasting quite long after a natural infection, and we expect that from the vaccination as well,” Culver said.
If experts decide it is too early for boosters, the extra shots may be instead be recommended nine months to a year after the first dose is administers, depending on how long antibodies are found to last, Salata added.
If the booster shot is eventually authorized, distribution processes may look different than the spring 2021 push for vaccinations, Culver said.
“My suspicion is we won’t be pushing it to happen quite as quickly, if we do go down that road. I also suspect we will be able to have even more distribution centers than we did previously,” he said.
