Moderna COVID-19 vaccine up to 100% effective in teens: What comes next

Moderna's COVID-19 vaccine is up to 100-percent effective in adolescents aged 12 to 18, a new study has found, with the pharma company planning to request permission from the US FDA and others to extend immunization to younger people. Currently, Moderna's drug is being distributed under an FDA emergency use authorization (EUA) in America, though only for adults aged 18 or above.

This new Phase 2/3 study, however, looked at its potential efficacy among a younger cohort of people. 3,732 adolescents were given ether two doses of Moderna's vaccine, mRNA-1273, or a placebo drug, and then the occurrence rate and severity of any COVID-19 cases recorded.

No coronavirus cases were recoded in the vaccinated group, after two doses, with Moderna concluding a 100-percent efficacy from 14 days after the second dose – the generally-accepted point at which people can be considered "fully vaccinated." Among the placebo group, 4 cases of COVID-19 were recorded.

Those numbers were based on the current standards for adult studies into coronavirus vaccine efficacy. Given younger people are typically less impacted by COVID-19, new, milder symptom metrics have also been developed, based on the US CDC's criteria. On those, tougher criteria, Moderna says, its vaccinated group still saw 93-percent efficacy, based on a single COVID-19 symptom and a single positive nasal or throat swab test result,

As for vaccine side-effects in adolescents, Moderna says that mRNA-1273 was "generally well tolerated" and showed similar issues among those injected as in the adult trials. Pain where the injection had been administered was the most common, along with headache, fatigue, and symptoms similar to a strong cold or flu after the second shot.

Moderna will monitor its adolescent cohort for 12 months to track long-term effects and effectiveness of the vaccine. However it plans to submit its results to regulators globally in early June. Then, it's hoping the US Food and Drug Administration (FDA) will extend its existing authorization so that younger people can begin to be vaccinated with mRNA-1273. Assuming the FDA agrees, it would come down to the CDC updating its own administration guidance so that individual states could get underway.

That would follow Pfizer-BioNTech's extension of its EUA in early May. The FDA agreed that the drug company's research suggested its vaccine was effective for young people aged 12-15, and broadened its guidelines for use as a result. Pfizer-BioNTech's drug had already been authorized for people aged 16 or above.

The potential impact of COVID-19 on younger people has been a controversial topic during the pandemic, with false assumptions from some quarters that adolescents were unable to contract coronavirus at all. In fact, the research suggests, younger people are at risk but often show milder symptoms, at least with the early-identified variants of the virus. However they can still be infectious to others, presenting a considerable risk to community spread in environments like schools, hence the urgency to expand vaccinations to include them.