The CDC has announced that older adults aged 65 and up, as well as those with weakened immune systems, can now receive a second dose of the updated versions of the Pfizer-BioNTech and Moderna Covid booster shots. The agency has recommended that people wait at least two weeks after their first dose before getting the second dose, and that those immunocompromised should wait at least two months. Vaccination is the best way to protect against the virus, but it is not 100% effective, so people should still take precautions such as wearing a mask and social distancing.