When the nation’s second-largest school district reopens for business despite tens of thousands of positive coronavirus tests among students and staff, things have changed.

When the state of California, which led the nation in caution, tells medical staffers who tested positive to go back to work if they’re asymptomatic, things have changed.

We are two years into a pandemic that has killed roughly 5.5 million people globally and altered life in ways big and small. Last January I wrote a column suggesting there was hope for a turnaround because the best medicine available — vaccine — was being pumped into arms everywhere.

So where do we stand now?

I’ve been trying to figure that out and would love to give you a definitive answer. But going forward, the virus will give us new looks and we’ll have to adapt.

Generally speaking, we’re in much better shape than we were two years ago. And better shape than we were a year ago, when getting the vaccine involved a mad scramble to nail down a place in line at a drug store or supermarket.

“I’m very much an optimist,” said Dr. Kimberly Shriner, an infectious disease specialist at Huntington Hospital in Pasadena.

But don’t take that as an invitation to throw a party and invite everyone you know.

“We have to be very humble in the presence of this virus,” Shriner added.

The vaccine doesn’t prevent infection, just as the flu vaccine doesn’t necessarily keep you from getting the flu. But you’re likely to have an easier time of it.

Another key advance is the rollout of a COVID-19 treatment drug called Paxlovid, which Kim-Farley called a game changer. Used promptly, said Dr. Robert Kim-Farley of the UCLA Fielding School of Public Health, “there’s an 88% reduction in hospitalization and death.”

We also now have a rapid antigen test, and “that didn’t exist a year ago,” Kim-Farley said. But we need far more of them to help us know whether we’re contagious to others.

The L.A. Unified School District’s decision to reopen schools led to more than a bit of chaos last week, with 62,000 students and staff out after testing positive. The district reported about 135,000 student absences on Jan. 11.

But Kim-Farley endorsed the decision to reopen.

“We know that children suffer if they’re not in the classroom, and remote learning, though better than nothing, is not a very good substitute for being in the classroom,” Kim-Farley said. “We also have new tools in our hands for students, including the vaccines we’re now able to give them.”

If schools everywhere can do more weekly testing and can move quickly to improve ventilation and air filtration systems, Kim-Farley said, the risks will be further minimized.

When I spoke to Shriner, she had just checked on patients in Huntington’s “long COVID” clinic.

“Our youngest patient is 26, the oldest are in their 70s,” she said, and long COVID — also known as post-acute sequelae of COVID — has been seen in children as well. Her patients have blood clots, inflammation of the brain, heart and lungs. Some have brain fog, some have gotten better and returned to work, some have not.

All the more reason to vaccinate, mask and distance, and to enjoy the freedoms that come with those precautions.

I asked Shriner how often she is asked by friends, family or colleagues for advice on do’s and don’ts. Every day, she said, and she tells people to pretend they have 10 risk cards.

“If you want to attend a football or baseball game, you have to ask if that’s where you want to spend a risk card,” Shriner said. “Travel right now is very dangerous, but some people have to do it. If you have a loved one who’s in a bad way, you may have to use a card for that.”

If she’s outdoors walking her dog, Shriner told me, she drops her mask. But if someone comes close, she pulls it back up.

“I don’t come from the ‘everybody’s going to get it school.’ I don’t want to get it. It doesn’t look like fun,” Shriner said. “I’m not going to be locked up, but I’m going to be sensible. … I think we can be hopeful because we’ve conquered all kinds of obstacles in the past. This is just going to take time, patience, equity and selflessness.”

So maybe you can breathe a little easier than you could at the start of 2020 or 2021.

But don’t let your guard down yet.