Dr. Salma Elfaki is studying 16-year-old Diego Alvarez, a patient in a clinical trial of the Moderna COVID-19 vaccine for adolescents conducted by Accel Research Sites with the Nona Pediatric Center in Orlando, Florida on September 25, 2021.

Paul Hennessy | SOPA pictures | LightRakete | Getty Images

Pfizer’s Covid vaccine is 93% effective at protecting against hospitalization in 12-18 year olds, the Centers for Disease Control and Prevention said in a small study published Tuesday.

The CDC tracked 464 Covid patients ages 12 to 18 in 19 U.S. children’s hospitals from June to September when the Delta variant was on the rise across the country. While about 72% of them had at least one underlying condition that increased their potential for severe symptoms, the researchers found that 97% of those who ended up in the hospital weren’t vaccinated.

“These data suggest that increasing vaccination coverage in this group could reduce the incidence of severe COVID-19 in the United States,” wrote CDC researchers in their weekly Morbidity and Mortality Report.

Six of the Covid patients were vaccinated and 173 were unvaccinated. Approximately 43% of critically ill children required intensive care and 16% of critically ill children received life support, with two deaths in the group according to the study.

The CDC’s results are similar to the results of a study conducted in Israel that found that Pfizer’s Covid vaccine was nearly 92% effective at preventing hospitalization in 12-15 year old patients. However, the Israeli study did not contain enough cases to properly assess the full effectiveness of the vaccine against Covid hospital admissions, the CDC wrote.

About 61% of the study participants were from the south, the CDC said, as the region had increased Covid transmission rates from June to September. The high concentration of patients from the south may also have affected the results, the researchers said.

The Food and Drug Administration approved Pfizer’s Covid vaccine on Aug. 23 for anyone over the age of 16 and left it in emergency status for children ages 12-15 pending further review. More than 104 million people in the US have been fully vaccinated with Pfizer’s vaccines, while over 9 million have already received a booster dose from Pfizer, the CDC reported Tuesday.

The CDC last month authorized Pfizer’s boosters for select risk groups, including those aged 65 and over, all medically vulnerable adults, and those who come into contact with Covid as a result of their work. U.S. health leaders have failed to approve boosters for those 12 to 18 year olds citing their high chances of surviving Covid and concerns about the risk of two vaccine-induced rare heart infections, myocarditis and pericarditis.

The researchers found that the study was limited by its small sample size, which prevented them from properly measuring the effectiveness of the vaccine in patients with underlying diseases. They added that they were also unable to determine the vaccine’s effectiveness against various variants of Covid, saying that some participants may have misrepresented their self-reported vaccination status.

Pfizer is currently waiting for the Food and Drug Administration to approve its vaccinations for children between the ages of 5 and 11. The company released data in September suggesting its two-dose vaccine regimen elicited a “robust” immune response in the younger pediatric age group, the FDA could clear the shots later this month.

The CDC reported that 46% of 12 to 15 year olds in the US were fully vaccinated against Covid, while 54% of 16 to 17 year olds had received a full dose series by Monday.