The announcement Wednesday that Moderna is seeking FDA approval to vaccinate young children is being met with excitement by many parents who have been eagerly waiting for the chance to help protect their kids from COVID-19. And while some local experts say they'll likely recommend the vaccine when it's available, they're worried the data on efficacy might not be enough to win over many other parents.

"We are very eager to get my three-year-old vaccinated," said Katie Kersey of West Roxbury. "He has some health issues that have made him high risk if he were to get COVID, so it's been a nerve wracking two years now."

When she heard Wednesday morning about Moderna's announcement, she said she was excited, but she's trying not to get her hopes up too much.

The efficacy results in kids in the new trial are notably lower than what was seen in Moderna's original trials in adults. The Cambridge-based company said in its announcement that a trial of about 6,700 young children showed 43.7 percent efficacy in children six months to two years old, and 37.5 percent efficacy in kids between two and six years old. The initial efficacy results for adults were about 94 percent.

"Yes, it's obviously a little disappointing compared to that," Kersey said. "But I'd still rather have 30 percent more protection for him than the nothing, you know?"

The company wrote in its press release that high fevers were the most common side effect for children, and that the frequency of the fevers was in line with other pediatric vaccines. It added that there were no cases of myocarditis, or heart inflammation, an extremely rare side-effect seen in some young adults, and no new side effects were identified.

But epidemiologists were quick to point out that the latest efficacy percentages also reflect how much the virus itself has changed over the last two years, becoming more contagious with new variants.

"We're not comparing those numbers to the original adult efficacy rate from 2020," said Dr. Shira Doron, the hospital epidemiologist at Tufts Medical Center. "We are comparing those numbers to estimates of the current effectiveness of Moderna vaccine against omicron in adults, which we know to be a lot lower."

Doron said she'd like to see the FDA reframe the goal of the COVID-19 vaccination program and move away from a focus on preventing infection.

"The only realistic goal is prevention of severe disease," she said. "And if that's the case, then it makes it even easier to accept efficacy in the 30s and 40s against any infection. Because if it's got that kind of efficacy against any infection, what we've seen is consistently greater efficacy against severe disease, hospitalization and death. And, of course, that's what matters the most."

"The efficacy, while it doesn't sound great, is actually roughly in line with the efficacy that we sometimes see from the seasonal flu vaccine," added Stephen Kissler of the Harvard T.H. Chan School of Public Health. "And that also can be very helpful for young kids to keep them from getting really sick from the flu. So I think that there is precedent for using vaccines of about this efficacy in young kids. And while of course I would love to see a 100-percent efficacy in all of the vaccines that we have available, I do still think it's high enough to be pretty useful."

The actual goal of the new Moderna trial was not to determine its efficacy in preventing infection, said Mark Pasternack, chief of pediatric infectious disease unit of Massachusetts General Hospital for Children.

"The end point of the study was to demonstrate vaccine immunogenicity — that is, did the vaccine raise antibodies?" Pasternack said. "And the vaccine did its job. It raised antibodies."

But he worries the vaccine may be a tough sell for some families and that some parents might not see the benefit.

"The nature of the illness, the epidemiology and the clinical features in young children is that severe disease is rare," he said.

Roberto Jiminez-Rivera of Chelsea said one benefit of vaccinating his 20-month old son would be the reassurance that it would reduce the spread of the virus in his community. Also, he said, it would mean he might now feel comfortable taking a family visit to Puerto Rico, where he grew up.

"My parents still live there. Most of my family is still there, and we have not been able to take our baby to Puerto Rico to visit my family," he said.

Jiminez-Rivera said he trusts the long history of safe and effective vaccines. What worries him, he said, is what's unknown about the long-term impacts of COVID infections.

"I think because of that uncertainty, we have made the decision to just be extremely careful about it, particularly with with our son," he said.

For Rachel Loischild of Roslindale, it was the personal toll of the pandemic that led to caution with her four-year-old.

"We are a family — one of, obviously, millions of families — that have lost a loved one to COVID, and so I take it very seriously," she said.

Getting her son vaccinated would be a relief, she said.

"I'm hopeful that I'll be less anxious about the worst possible outcomes if he does get COVID."

And she said she'd like to serve as an example to other parents she knows who have their doubts.

"I am shocked by the number of people who have still not vaccinated their eligible children [over age five]," she said. "And I think they need their community around them to say 'Yes, this is safe. Yes, I'm I'm wanting my kid vaccinated. Yes, this is the best thing to do for, for me, for you, for everyone in our society.'"

Just over half of Massachusetts children between 5 and 11 years old have gotten at least their first dose, according to state data.

Loischild said she thinks getting her son vaccinated would help return the life of her family to something closer to normal.

"I'm not quite ready to say, 'yes, my kid's vaccinated, we'll be 100 percent back to normal.' But it gives us a better shot at it," she said. "You know, I haven't been to dim sum in three years. I miss it, you know? Have you found outdoor dim sum? I haven't."