Pfizer and BioNTech are giving an early look at clinical trial data for their Covid-19 vaccine in children 12 to 15 years old and the results so far look better than the efficacy shown in older teens and young adults.

The vaccine partners said Wednesday that the preliminary data from a Phase 3 study show the messenger RNA vaccine was 100% effective at preventing infection and produced robust antibody responses. The data are preliminary and have not yet been published in a peer-reviewed journal. But effiicacy so far is comparable to the 95% efficacy reported in tests in adults. Pfizer and BioNTech said that based on these encouraging early results, they plan to ask the FDA to amend the vaccine’s emergency use authorization “as quickly as possible” to include this younger age group.

The initial FDA authorization for the Pfizer and BioNTech vaccine in adults also included those 16 and 17 years old. Pfizer and BioNTech said the submission to regulators seeking authorization in younger teens would be made in coming weeks, which could make the vaccine, called BNT162b2, available to them before the start of the next school year.

The Phase 3 study enrolled 2,260 adolescents in the U.S; 1,131 participants received the vaccine and 1,129 were given a placebo. The study produced 18 cases of Covid-19, all of them in the placebo group. The results also showed that vaccination elicited neutralizing antibodies at levels comparable to what was reported in earlier clinical tests in individuals 16 to 25 years of age.

“The initial results we have seen in the adolescent studies suggest that children are particularly well protected by vaccination, which is very encouraging given the trends we have seen in recent weeks regarding the spread of the B.1.1.7 U.K. variant,” BioNTech CEO Ugur Sahin said in a prepared statement.

Pfizer and BioNTech said that the younger age group tolerated the vaccine well, showing side effects consistent with those observed in the older group. Those side effects included pain at the injection site, fatigue, headaches, muscle pain, chills, joint pain, and fever. The companies added that all participants in the study will continue to be monitored for safety for two years after their second dose.

The vaccine partners plan to submit these clinical trial results for peer review and potential publication in a scientific journal. The companies are also pressing forward with tests of their vaccine in younger children, ranging from 6 months to 11 years of age. Last week, a global Phase 1/2/3 study enrolled dosed its first healthy participants to first assess safety in younger children. The study is split into three groups: children 6 months to 2 years of age, 2 to 5, and 5 to 11. Participants will receive two doses three weeks apart. The 5- to 11-year-old group started dosing last week. The companies plan to start dosing in the 2 to 5 group next week.

So far, three Covid-19 vaccines have emergency authorization in the U.S., two of them based on mRNA technology, which delivers messenger RNA with the genetic instructions for the spike protein of the novel coronavirus. The protein-making machinery of cells uses those instruction to produce copies of the spike protein, which prompts an immune response that confers immunity.

The other mRNA vaccine, from Moderna, is authorized for those 18 and older. The Cambridge, Massachusetts-based biotech has completed enrollment in a a Phase 2/3 study in about 3,000 adolescents. Earlier this month, the company began another study testing the vaccine in children 6 months to 12 years of age. That study is enrolling about 6,750 children in the U.S. and Canada.

Johnson & Johnson’s single-shot Covid-19 vaccine, which a viral vector vaccine, is authorized for those 18 and older.

Photo by BioNtech