It’s been two years since we first started hearing about a novel coronavirus that was sweeping the globe. As our knowledge of how the virus works advances, and the virus itself takes on new forms, the public health guidance to control it changes.

That’s the way it’s supposed to work. When you get more information or the circumstances change, you change your mind.

But too many people see the evolving science as proof that the doctors don’t know what they are doing. Rather than listen to what the Centers for Disease Control and Prevention or other public health authorities advise, people are apparently making up their own rules, which they follow when they want to.

It’s easiest to see when it comes to wearing masks. Some businesses require them; others just recommend them. Some people wear them all the time, others as little as possible, while a few still think they are compromising by covering their mouths but not their noses.

Considering all of these disparities, you might think that the health advice when it comes to the use of masks has been vague or confusing, when it has actually been one of the constants.

Like the other strains, omicron is an airborne virus that most commonly spreads among people in close contact with each other, according to the CDC. The virus spreads when people inhale the tiny droplets released when infected people cough, sneeze, talk, laugh or breathe.

Vaccines have proven to be highly effective at preventing serious illness and death, but vaccinated people can still get infected and transmit the virus. So even in Maine, where more than 75 percent of the population is fully vaccinated, public health authorities recommend that vaccinated as well as unvaccinated people wear masks when they are indoors in public settings where there is a high rate of transmission – which, right now, includes all 16 Maine counties. Some research calls for double masking or wearing masks that are built with multiple layers of filtration, instead of the simple cloth masks that had previously been recommended.

These changes are not proof that vaccines don’t work, or that public health authorities can’t make up their minds.

What has changed is the omicron variant, which was first discovered in late November. The new strain has already become the dominant cause of COVID worldwide as well as being one of the most contagious viruses ever known to science.

For the last year, vaccination has been the No. 1 weapon in the fight against COVID, but not everyone can be vaccinated, and even vaccinated people can catch and spread the virus.

That’s why everybody should follow the same simple rules around mask wearing, at least until the level of transmission drops to a safe level.

It seems like we have been living with this for a long time, but COVID is still a new disease, and we shouldn’t be surprised if we learn more about it and that changes the guidance.

We all should know the rules by now, and it’s up to each of us to follow them.