In this May 12, 2021, file photo, one man holds the door for another as they arrive at a COVID-19 vaccination clinic at the Auburn Mall in Auburn, Maine. Credit: Robert F. Bukaty / AP

An increasing number of fully vaccinated people in Maine with COVID-19 are filling ICU beds across the state. Yet those numbers are more representative of Maine’s high vaccination rate than the ineffectiveness of the vaccine, according to health officials.

About 30 percent of those with the coronavirus being treated in the ICU at Northern Light’s 10 hospitals were vaccinated as of Tuesday morning. Four out of 13 patients on ventilators were also vaccinated — about 30 percent.

While waning immunity could play a role, the far more significant reason for the number of vaccinated patients appears to be the numerical reality of Maine’s high vaccination rate, Maine Center for Disease Control and Prevention Director Nirav Shah said Wednesday. Maine has the third highest rate of fully vaccinated people in the country, a factor that is undoubtedly leading to more hospitalized vaccinated people.

“It’s a rather insidious and somewhat ghoulish byproduct of the fact that we are really vaccinated,” Shah said.

While the numbers are evidence of Maine’s successful vaccine efforts in comparison with other states, it could provide impetus for state health officials as they encourage newly eligible people to get a COVID-19 booster shot.

Those shots were approved by the U.S. Centers for Disease Control and Prevention for at-risk groups last week. Many of the groups newly eligible for the booster shot, including those over 65 and adults with underlying health conditions, are the people most likely to be hospitalized from a breakthrough case of COVID-19.

From Aug. 27 to Sep. 24, about 30 percent of new coronavirus hospitalizations in Maine (48 out of 159) were of vaccinated patients, according to Maine CDC data. About 0.1 percent of vaccinated people were infected with the virus during that period compared with 2.3 percent of those who are not fully vaccinated.

About 920,000 Mainers have received at least one dose of the vaccine, far outnumbering eligible people who have not or those under 12 ineligible for the vaccine (425,000). As the number of vaccinated people in Maine has risen, it’s made it more likely that they would appear in ICU data, Shah said.

However, Shah said it was a possibility that “waning immunity” could also be playing a role, especially for those who already have pre-existing health conditions. He said it may show the potential helpfulness of booster shots and extra vaccine doses, 16,520 of which have been administered across the state.

Dr. James Jarvis, COVID-19 senior physician executive with Northern Light Health, noted that the vast majority of hospitalizations within the hospital system were still among unvaccinated people.

“The vaccine is still clearly our best way out of this pandemic,” Jarvis said.

Even as it begins to more thoroughly consider the idea of waning immunity from the vaccines and the use of booster shots, Shah said the Maine CDC continues to be focused on administering first doses to the 265,000 eligible people across the state who had yet to receive a single dose as of Wednesday.

“If folks don’t go out and get vaccinated, particularly in the near term, we’re going to continue to see regions of the state with really high transmission rates,” Shah said.

BDN writer Jessica Piper contributed to this report.