Craig Moore of Sumner gets a bandage after his first dose of the Moderna COVID-19 vaccine from Everett Flannery, paramedic with Redington-Fairview EMS, at the Skowhegan State Fair on Aug. 20, 2021. Credit: Linda Coan O'Kresik / BDN

AUGUSTA, Maine — More fully vaccinated Mainers are testing positive for COVID-19 as the virus spreads rapidly in a state where 65 percent of the population is fully vaccinated, but vaccines are still dramatically reducing the risk of infection and hospitalization.

The Maine Center for Disease Control and Prevention is reporting 1,818 breakthrough COVID-19 cases, accounting for about 0.2 percent of the more than 870,000 fully vaccinated people here. Notable cases include that of U.S. Sen. Angus King, who said Tuesday that he was symptom-free after contracting the virus earlier this month.

Caseloads among unvaccinated Mainers still account for nearly all of the recent COVID-19 occurrences making up the surge. The state has seen more than 38,000 cases among unvaccinated people since late January, when the first Mainers became fully vaccinated, accounting for about 2.8 percent of the population.

Those numbers indicate the vaccine has been more than 90 percent effective in preventing infections here, though vaccine boosters are still likely on the horizon and are likely to further reduce risk for the Mainers most likely to be affected by breakthrough cases.

The recent state data suggest unvaccinated Mainers are about eight times as likely as vaccinated people to test positive for COVID-19, Maine CDC Director Nirav Shah said Monday. There have also been 89 virus-related hospitalizations among fully vaccinated people and 29 deaths, according to state data, compared to 828 hospitalizations and 214 deaths among unvaccinated people since late January, according to state data.

Maine collects more data on breakthrough cases than the U.S. Centers for Disease Control and Prevention, which is only tracking infections among the fully vaccinated that result in hospitalization or death.

But Maine’s rates for breakthrough COVID-19 cases, hospitalizations and deaths are comparable to other states that collect similar data, with less than half of one percent of fully vaccinated people testing positive in nearly every state, according to the Kaiser Family Foundation, a nonprofit that tracks health data.

Breakthrough cases also do not affect everyone equally. Nearby Vermont has the highest vaccination rate of any U.S. state, with 77 percent of adults fully vaccinated, according to federal data. At the University of Vermont Medical Center in Burlington, about a third of COVID-19 patients are fully vaccinated, said Dr. Timothy Lahey, an infectious disease physician there.

But nearly all of those vaccinated patients are “medically fragile” in some way that explains why vaccines aren’t working fully for them, Lahey said. Organ transplant recipients, cancer patients and others taking immunosuppressant medications are less likely to develop antibodies from COVID-19 vaccines.

In recognition of the diminished vaccine effects for immunocompromised individuals, the U.S. CDC began recommending third shots for a limited number of people earlier this month. The agency will recommend boosters beginning next month for more people eight months after completing their first vaccine course.

Booster shots are “probably a good idea” said Dr. Robert Horsburgh, an epidemiology professor at Boston University, but convincing people who have not yet had the vaccine to get their first doses would still do more to stop the virus’ spread and reduce hospitalizations.

“What’s going on right now is that people who aren’t vaccinated and who get infected are getting pretty sick,” Horsburgh said.

BDN writer Michael Shepherd contributed to this report.