Covid-19 herd immunity is a difficult target, experts warn, but vaccinating teens could be key to protecting us this fall

The United States is offering up freebies, expanding the pool of those eligible and shifting access to local pharmacies in its attempts to encourage vaccine holdouts to get inoculated against Covid-19. In the last six months, nearly 150 million people in the US have received at least one dose of a Covid-19 vaccine in what is the fastest and largest mass vaccination effort in world history. Still, the US vaccination rate has declined from its peak last month, pushing officials to offer new incentives, known as carrots, to further encourage the wary, hesitant and inaccessible to get vaccinated. Some of those carrots are access to cultural events.