US pharmaceutical and biotechnology company Moderna Tuesday announced that it has started COVID-19 vaccine trials for children aged six months to 12 years old, with plans to enroll about 6,750 participants.

"We are pleased to begin this Phase 2/3 study of mRNA-1273 in healthy children in the US and Canada," said Moderna's CEO Stephane Bancel in statements.

"This pediatric study will help us assess the potential safety and immunogenicity of our COVID-19 vaccine candidate in this important younger age population."

Notably, US health officials stated that less children have been ill from the virus compared to older demographics, however, they can indeed be infected and can transmit the virus.

Most infected toddlers and children have mild symptoms or no symptoms at all.

Moderna said 17.8 million adults in the US have received their vaccine, as the country seeks to step up its innoculation program against the pandemic that has killed over 535,000 people statewide.

The Pfizer, Moderna and Johnson & Johnson vaccines have all been authorized for emergency use, and the companies are set to deliver more than enough to cover the entire US adult population by mid-year.

The United States is currently vaccinating around 2.2 million people per day, and almost 65 percent of Americans aged 65 and older have had at least their first vaccine dose.