If there’s one thing to take away from the barrage of new information on the delta variant and new masking recommendations, it’s this: public health experts say vaccines are Maine’s best tool in the fight against COVID-19.

But getting some people fully on board isn’t as direct.

“I think that’s what people are very hesitant to do right now, is trust,” Joanne Kenny-Lynch, system director of infection prevention at Central Maine Healthcare, said Tuesday.

Internal documents from the U.S. Centers for Disease Control and Prevention that were leaked to The Washington Post last week threw distrust in vaccines — which has been around long before COVID-19 — into greater focus.

What’s more, Maine’s latest masking recommendation, which follows the U.S. CDC’s, is less than straightforward. It says that all people, regardless of vaccination status, should wear masks indoors in areas with substantial or high rates of transmission.

The U.S. CDC uses two metrics to determine a county’s transmission level: The total number of new cases over the past seven days per 100,000 residents and the testing positivity rate. Depending on the range those metrics fall into, counties are rated as having either a low, moderate, substantial or high transmission rate.

If the two metrics indicate different levels of transmission, the higher of the two is used.

The tri-county region of Androscoggin, Franklin and Oxford counties had a moderate level of community transmission Tuesday, according to designations from the U.S. Centers for Disease Control and Prevention, meaning that mask-wearing is not necessarily recommended for all people, regardless of vaccination status, in indoor settings.

Four counties — Lincoln, Penobscot, Somerset and York — had substantial levels of community transmission, and Waldo County had a high level, meaning that the masking recommendations were in place there.

Also on Tuesday, state health officials reported 255 additional cases of COVID-19 since Saturday, including 20 new cases in Androscoggin County, three in Franklin County and six in Oxford County.

There were no additional deaths.

This system can be confusing and complicated, especially in rural areas where transmission rates can change drastically from day to day, but it remains one of the best tools for monitoring and predicting surges, Dr. Dora Anne Mills, chief health improvement officer for MaineHealth, said Tuesday.

“When you get to rural areas, rural counties, one of the challenges is just the pure numbers,” said Mills, who served as Maine CDC director for more than 14 years, until 2011.

“Your denominator that is the population is statistically small enough that even small variations in disease,” such as a few new cases of the disease, could “cause that county to flip from low to high, or low transmission to high transmission, pretty easily,” she said.

There are ways to potentially get around this, such as taking the 14-day or 28-day cumulative case count instead of the seven-day, but Mills said that lowers communities’ reaction times when there are spikes in cases.

“I think at this point in time, with the delta variant, it’s better to err on the side of having categories that do change more rapidly than more slowly because the delta variance is so much more contagious that you don’t want to wait until, necessarily, the 28-day rate or the 14-day rate goes up significantly,” she said.

The delta variant accounted for about 60% of new cases in Maine, according to a Maine CDC report published earlier this week. As of July 30, there were 75 cases of the delta variant in Maine confirmed through genome sequencing.

Maine CDC Director Dr. Nirav Shah said last week that the delta variant is one of the primary reasons behind the shift in masking recommendations. The variant, a mutation of the original COVID-19 virus, is about two times as contagious, he said.

The leaked U.S. CDC documents said the delta variant appears to spread as easily from a fully vaccinated person as an unvaccinated person and officials expressed concerns that that, along with the rise of so-called “breakthrough cases” — instances in which a fully vaccinated person contracts the disease — could lessen the public’s trust in vaccines.

“I’d love to see a very complicated process explained simply so that people could understand it and … feel like they could trust this vaccine,” Kenny-Lynch, from CMH, said.

What is perhaps missing from the conversation on the delta variant and the effectiveness of the vaccine is a fundamental understanding of the way that viruses work.

“Viruses have one goal and that’s really to survive,” she said. “And the more of a chance that we give that virus to replicate in our communities and our environment, the higher chance we have for seeing different mutations or different variants.”

And although there are more breakthrough cases “because we’re having so much circulation of COVID still in our communities,” the overwhelming majority of new cases, hospitalizations and deaths in Maine are among unvaccinated people, Kenny-Lynch said.

“The vast majority of our cases coming in and being hospitalized with severe illness are those that are not vaccinated.”

Mills, from MaineHealth, put it another way.

“The efficacies (of the vaccines) with the COVID strains from last fall were so high that we had all these tremendous expectations of this pandemic just kind of melting before our eyes because of the fact that the efficacies were just astounding from last fall,” she said.

“But the issue was that did change. The issue was that the virus evolved and mutated, and viruses do find every little nook and cranny they can to become more adapted.”

Proactive measures, such as the latest masking recommendations, are needed “to stay a few steps ahead of it,” Mills said. “But the good news is that vaccines do work.”

The big picture, Kenny-Lynch said, “is to get the vaccinations, to get the number of people who are infected in our communities down and stop the mutation of this virus.”

Vaccinations are about protecting ourselves and everyone around us, she said, “but if this thing keeps spreading around, we’re going to see some really funky other variants potentially come out.”