Three weeks after a federal official said Moderna was struggling to find adolescent volunteers for its latest COVID-19 vaccine study, the Cambridge biotech says enrollment has picked up and it expects to have results of the clinical trial around the middle of the year.
Moderna became the second drug maker to have a coronavirus vaccine cleared for emergency use, on Dec. 18, but the Food and Drug Administration restricted it to people 18 and older, the age range of participants in the firm’s late-stage trial. Pfizer-BioNTech had received the first authorization a week earlier, but it covered people as young as 16 because that vaccine was tested on some 16- and 17-year-olds and deemed safe.
Now, as states slowly roll out both vaccines, Pfizer-BioNTech and Moderna are starting to test their two-shot vaccines on adolescents. Pfizer finished enrolling its nationwide study last month, recruiting 2,259 volunteers between the age of 12 and 15, according to a company spokesman. Moderna is still recruiting 3,000 volunteers age 12 to 17.
Dr. Moncef Slaoui, who recently stepped down as the scientific head of the federal vaccine program Operation Warp Speed, told USA Today in a Jan. 12 story that not enough adolescents were signing up for Moderna’s study, but he gave no reason and declined to share specifics.
Colleen Hussey, a Moderna spokeswoman, said late last week that enrollment was slow during the holiday season but has picked up.
“We have seen an increase in enrollment and interest in participating the trial so far this year at our sites around the country,” she said in an e-mail, declining to provide specifics. “We continue to bring clinical trial sites online and we are on track to provide updated data around mid-year 2021.”
The government-run website clinicaltrials.gov lists 10 sites around the country recruiting participants and another 15 waiting to start.
Imran Khan, who manages a Houston trial site at CyFair Clinical Research Center, said he heard in a conference call of site managers last Thursday that the study had enrolled about 820 participants so far. CyFair began testing the vaccine a month ago, he said. The center initially administered shots to a couple of kids a day but has hired more staff and is now up to eight or nine youngsters daily, including Saturdays. “We’re pretty booked,” he said.
Hussey declined to confirm the figure of 820.
The only Massachusetts site participating in Moderna’s study is at the University of Massachusetts Medical School in Worcester. Dr. Katherine Luzuriaga, principal investigator there, said she expects to start testing the vaccine in a week or two.
“We’ve had very robust interest from the community,” she said.
Luzuriaga acknowledged that researchers often face challenges recruiting participants for pediatric trials because of children’s busy school and extracurricular schedules, the cost of transportation to and from trial sites, and fears many youngsters have about getting shots.
Luzuriaga, who directs the UMass Center for Clinical and Translational Science, said her center is trying to accommodate adolescents’ schedules by scheduling some evening and Saturday appointments. Moderna is providing a stipend at trial sites to cover transportation costs and other expenses.
The trial is testing the same Moderna messenger RNA vaccine that the government cleared for emergency use in adults. Volunteers will receive two doses four weeks apart. Two-thirds of adolescent participants will get the vaccine, while the remainder will receive a placebo. Neither the researchers nor volunteers will know who received the vaccine until later in the study. Researchers will keep in touch with participants for a year after the second shot to see how they fare.
Moderna is planning another study for children between the ages of 6 months and 11 years old.
“Developing the evidence base for use of this vaccine in children and adolescents is incredibly important,” said Luzuriaga, whose center also participated in Pfizer-BioNTech’s late-stage international study of nearly 44,000 adult volunteers that led to that vaccine’s FDA authorization. “We’ve done quite a bit of outreach to get the word out.”
Luzuriaga, like other principal investigators interviewed by the Globe, said Moderna asked her not to share how many adolescents have applied to participate in the new trial and how many her site will accept.
One of the potential challenges facing recruiters may be the fact that most adolescents infected with the coronavirus suffer only mild illnesses or show no symptoms. As of Monday, less than 12 percent of cases in the United States occurred in people under the age of 18, according to the Centers for Disease Control and Prevention. And 0.2 percent of deaths involved people under that age.
Nonetheless, adolescents can become seriously ill from COVID-19. Indeed, the CDC is investigating a rare but serious medical condition associated with cases in children called “multisystem inflammatory syndrome.” The condition is marked by inflammation in multiple organs and can be deadly if not treated promptly.
But immunizing children is vital for reasons that go beyond their own health. Adolescents, even if asymptomatic, can infect older people and others who have underlying conditions that make them especially vulnerable. And young people have shouldered a heavy burden during the pandemic, with many having to switch to online learning and give up extracurricular activities.
Dr. Gary Berman, principal investigator of Moderna’s study of the vaccine in adolescents at Clinical Research Institute in Minneapolis, said his site has been dispensing shots to volunteers six days a week, 10 hours a day, for a month. His waiting list is so long that he had to stop adding names.
“People really want to get their lives back in order,” said Berman, an allergist and immunologist. “I could put in as many patients as Moderna would let me.”
Many participants, he said, are the children of pediatricians whose practices he contacted to recruit volunteers. “If I send a letter to a pediatrician, the hope is that they would tell their patients to participate,” he explained. “But they’re also the first people to know.”
Berman said adolescent volunteers have tolerated the vaccine well, with only some mild side effects, including soreness at the injection site or a low-grade fever that passes quickly.
Pfizer began enrolling adolescents in its trial in October and expects to have results by the middle of the year, according to Steven Danehy, a spokesman for the New York-based drug giant. Neither of the two Massachusetts sites that participated in the study of adults ― UMass Worcester and Boston Medical Center ― are testing the Pfizer vaccine on adolescents. Danehy was unaware of any other sites in the state involved in the study.
Both the Pfizer-BioNTech and Moderna vaccines are powered by a cutting-edge technology called synthetic messenger RNA. The shots inject messenger molecules that teach cells to create the distinctive spike protein on the surface of the coronavirus. When cells make the protein, it stimulates an immune response that protects people from the virus.
Both the Moderna and Pfizer-BioNTech vaccines protected about 95 percent of recipients from the coronavirus in large late-stage studies.
Jonathan Saltzman can be reached at email@example.com.