Four states have fully vaccinated at least half of their population against the coronavirus, according to data published Sunday from the Atlanta-based Centers for Disease Control and Prevention.

Connecticut, Maine, Massachusetts and Vermont have reported vaccination rates of at least 50%, according to the CDC data.

A total of 21 states are reporting total population fully vaccinated rates of more than 40%. Georgia’s vaccination rate was 30.7%, one of the nation’s lowest. Mississippi, according to the data, has the nation’s lowest vaccination rate, with 26.5% of its total population fully vaccinated. Alabama was the only other state to report a total population vaccination level of less than 30%.

When it comes to the total population numbers that have received at least one vaccination dose, 21 states and the District of Columbia are reporting vaccination rates of 50% or more: California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Vermont and Washington state.

Almost 39% of Georgians, according to the CDC, have received at least one dose of the vaccine. Again, Mississippi registers the lowest percent of residents who have received at least one dose, with 33.2%.

New coronavirus cases across the United States have tumbled to rates not seen in more than 11 months, sparking optimism that vaccination campaigns are stemming severe COVID-19 cases and the spread of the virus.

As the seven-day average for new cases dropped below 30,000 per day last week, CDC Director Dr. Rochelle Walensky pointed out cases have not been this low since June 18, 2020. “As each week passes and as we continue to see progress, these data give me hope,” Walensky said Friday.

Health experts credit an efficient rollout of vaccines for the turnaround. But demand for vaccines has dropped across much of the country. President Joe Biden’s administration is trying to convince other Americans to sign up for shots, arguing vaccines offer a return to normal life.

White House health officials on Friday even waded into offering dating advice. They are teaming up with dating apps to offer a new reason to “swipe right” by featuring vaccination badges on profiles and in-app bonuses for people who have gotten their shots.

Ohio, New York, Oregon and other states are enticing people to get vaccinated through lottery prizes of up to $5 million.

A medical center in Louisiana reported Friday it has identified the state’s first two cases of a COVID-19 variant that has spread widely since being identified in India. The COVID-19 variant has been classified as a “variant of concern” by Britain and the World Health Organization, meaning there is some evidence that it spreads more easily between people, causes more severe disease, or might be less responsive to treatments and vaccines. The variant has also been reported in several other states, including Tennessee, Nebraska and Nevada.

Last week, the CDC said most people who have received the full course of shots and have no COVID-19 symptoms don’t need to be screened for the virus, even if exposed to someone infected.

The change represents a new phase in the epidemic after nearly a year in which testing was the primary weapon against the virus. Vaccines are now central to the response and have driven down hospitalizations and deaths dramatically.