Medical experts in Maine said mask-wearing remains key in reducing the spread of COVID-19 variants.“An ounce of prevention is a pound of cure. We need to make sure we take these steps to keep safe,” Northern Light Health Vice President of Pharmacy Matt Marston said.Marston added that vaccinations also remain the best tool against serious illness from COVID-19 and hospitalization.“The more people that get vaccine, the less likely we will see further variants take hold of COVID-19 and mutate and evade vaccine immunity, which is ultimately what we really worry about,” Marston said.MaineHealth Chief Medical Improvement Officer Dr. Dora Anne Mills said breakthrough cases among fully vaccinated people are a factor in the new federal mask guidance released on Tuesday.“They had very high concentrations of virus in their nose and mouth, so they are perhaps fairly contagious. We want to make sure we put on all the layers on if we can,” Mills said.On Wednesday, Maine aligned with the federal guidance, which recommends that vaccinated people in areas with substantial or high levels of community transmission wear masks in indoor public spaces. Mills said she often wears a mask in crowded indoor spaces with poor ventilation, despite being fully vaccinated.“Am I going to share breathed air with these people? Do I want to share breathed air with these people? That is the litmus test for me,” Mills said.