Moderna has reported that the Phase II/III TeenCOVE study of its Covid-19 vaccine (mRNA-1273) met the primary immunogenicity goal in adolescents, with immune responses similar to those seen in adults.

Co-developed with the National Institute of Allergy and Infectious Diseases’ (NIAID) Vaccine Research Center researchers, the Moderna Covid-19 vaccine encodes for a prefusion stabilised form of the Spike protein.

The US Food and Drug Administration (FDA) granted emergency use authorization (EUA) for the vaccine in people aged 18 years and above in December last year.

The Phase II/III TeenCOVE trial enrolled about 3,732 subjects aged between 12 and 18 years in the US. The participants were randomised in a 2:1 ratio to receive two 100µg doses of the vaccine or placebo.

The trial’s primary goal, which was met, was non-inferior immunogenicity compared to Phase III adult study comparator group.

Data from the study also showed that no Covid-19 cases were seen in subjects who were given two doses of the vaccine versus four cases reported in the placebo arm.

The company said that the vaccine efficacy was 100% beginning 14 days following the second dose. Meanwhile, a 93% vaccine efficacy was observed in seronegative subjects beginning 14 days after the first dose.

The vaccine was found to be well-tolerated and the safety and tolerability profile was in line with the Phase III COVE study in adult subjects.

Most of the adverse events were mildly or moderately severe with injection site pain observed as the common solicited local adverse event.

Moderna intends to submit the results to various regulators across the globe next month.

Moderna CEO Stéphane Bancel said: “We are encouraged that mRNA-1273 was highly effective at preventing Covid-19 in adolescents.

“We will submit these results to the US FDA and regulators globally in early June and request authorisation. We remain committed to doing our part to help end the Covid-19 pandemic.”

The company is gathering additional safety data and the subjects will be followed up for a year after administering the second dose to evaluate long-term protection and safety.

In a separate development, the FDA has updated its guidance, noting that it may not review and process new EUA requests for Covid-19 vaccines for the rest of the pandemic unless the companies have already initiated talks with the agency.