About 35 percent of Maine residents have been infected with COVID-19 from the pandemic’s onset through February, far below the national average of 58 percent, according to a new federal study.

Infections have ramped up since the delta wave last fall and omicron wave over the winter. But health officials said an effective response in the early days of the coronavirus pandemic likely helped keep Maine’s infection rate lower over the long term. As of September 2021, only 8 percent of Maine residents had been infected with COVID-19, compared with 29 percent nationally.

Through February, Maine had the third-lowest infection rate in the nation, behind only Hawaii at 34 percent and Vermont at 29 percent, according to the U.S. Centers for Disease Control and Prevention.

Dr. Nirav Shah, director of the Maine CDC, said in an interview Wednesday that many factors contributed to Maine’s low infection rate, including early measures to restrict large gatherings, residents staying apart and masking, and the effort to get Mainers vaccinated.

“We are not only one of the most vaccinated states, but the velocity with which we vaccinated was among the best,” Shah said. “Mainers lined up for their vaccines in droves.”

Shah said other states may have eventually caught up, but Maine’s relative quickness to vaccinate gave higher levels of immunity to large sections of the population within months of the vaccine rollout in spring 2021. Maine currently has a 75 percent vaccination rate for its population, the third-highest in the nation behind Vermont and Rhode Island, according to the Bloomberg News vaccine tracker.

Shah said most Maine people wanted to get immunized and avoid COVID-19.

“Mainers believe in science, and these numbers are the proof of that pudding,” Shah said.

Among the other New England states, 53 percent of the residents in Massachusetts and Rhode Island have been infected with COVID-19, along with 44 percent in Connecticut. There was not enough data in New Hampshire for the CDC to release a percentage.

Iowa had the country’s highest infection rate at nearly 71 percent, followed by Texas at roughly 70 percent.

The federal health agency based its study on blood testing in all 50 states and modeling that estimates that actual infections are about 2.4 times higher than reported case counts. In Maine, actual infections are estimated to be slightly more than two times the released case counts. Official case counts often miss asymptomatic cases or cases confirmed by at-home tests that are not reported to health departments.

Those ages 17 and under are most likely to have contracted COVID-19, with 75 percent becoming infected nationwide. Vaccine manufacturers have not yet produced a vaccine approved by the U.S. Food and Drug Administration for children under 5, and the latest estimate is that it will be at least until June before regulators approve a vaccine for the youngest children.

There was no infection rate estimate given for Maine children 17 and under due to insufficient sample sizes.

Dr. Cheryl Liechty, an infectious disease physician and epidemiologist with MaineHealth’s Pen Bay Medical Center in Rockport, said the fall and winter were difficult in Maine, with the delta wave followed by the omicron surge. But compared with other states, Maine weathered the storm well, she said.

“When the delta wave arrived in 2021, we had already achieved really impressive vaccination rates,” Liechty said. “In Maine, we did exceedingly well in 2020 pre-vaccine, and we’ve continued to do well relative to other states in the post-vaccine era.”

Early in the pandemic, aside from abiding by pandemic restrictions, Maine’s rural nature and dispersed population may have helped limit the spread of COVID-19, she said.

While there has been a lot of discussion about waning vaccine effectiveness and booster shots, including how many booster shots should be given to certain populations, the “majority of the benefit” to the immune system is from the initial doses of the vaccines, Liechty said. It’s also important which populations are getting boosted, and in Maine, there has been good uptake for boosters among seniors, who are most vulnerable.

Among Maine’s older population of roughly 391,000 residents 60 and up, 361,000 booster doses have been administered, according to the Maine CDC. About 682,000 booster doses have been administered to all of Maine’s 1.3 million residents. Only those 12 and older are eligible for boosters.

Maine reported 526 cases of COVID-19 on Wednesday. There were no additional deaths.

Since the pandemic began, Maine has recorded 243,128 cases of COVID-19, and 2,282 deaths. Hospitalizations increased from 132 on Tuesday to 136 on Wednesday, including 29 in critical care and 11 on ventilators.

Unvaccinated people represent roughly 67 percent of the COVID-19 patients treated in Maine hospitals since vaccines became readily available through April 15, according to the Maine CDC website.