I was invited to a vaccinated-only backyard pool party recently.

The hostess, Danyl S. Patterson, had warned guests that she wouldn’t be making exceptions, even for close friends who haven’t been inoculated.

“Some of the folks were upset and I knew they were going to be,” said Patterson, an attorney. “There was a whole bunch of restrictions.”

When it comes to the delta variant — a strain of COVID-19 that’s about 55% more contagious than the alpha variant — Patterson doesn’t like taking chances. So not only was her event a socially distanced affair but afterward she called partygoers to make sure no one had gotten sick.

Too bad more people aren’t as vigilant.

If they were, Philly’s COVID-19 situation wouldn’t be right back where it was this time last summer, thanks to an increase in new cases in recent weeks. COVID-19 cases doubled in Philadelphia between July 19 and Aug. 1.

On Tuesday, acting City Health Commissioner Dr. Cheryl Bettigole announced she was restarting weekly health department COVID-19 news conferences and urged Philadelphians to mask up indoors in public spaces, regardless of vaccination status.

“When you do get together with those who aren’t vaccinated, limit the numbers of people to lower your risk,” she cautioned. “Hold gatherings with children too young to be vaccinated outdoors or with masks on, and mask if you attend any kind of public indoor event.”

As I listened, I wished she’d made a bold announcement like NYC Mayor Bill de Blasio’s that the Big Apple would start requiring proof of COVID-19 vaccinations at gyms and for indoor dining.

» READ MORE: These are the Philadelphia restaurants that require proof of vaccination

I was happy to read how several local restaurants including Martha’s in Kensington opted to start requiring proof of vaccination status for indoor dining. It’s a small bit of peace of mind for staffers and restaurant-goers alike. The way it is now, dining out is like the Wild West. You go in knowing you’re taking your chances.

Philadelphia Fringe Festival organizers also are mulling the possibility of asking for proof of vaccination. And health department and city officials reportedly are in active discussions about Made in America, which is scheduled to return to the Parkway Labor Day weekend after being canceled last year because of COVID-19.

We should all be enjoying what’s left of summer instead of worrying about what sort of fresh hell fall might bring. But we can’t because certain folks won’t follow the science and get vaccinated.

A new study released Wednesday by the Kaiser Family Foundation revealed that not only are vaccine holdouts not convinced that the inoculations will help protect them from COVID-19, they are more afraid of the injection itself than they are of contracting the coronavirus, which is baffling.

I’m almost out of words when it comes to trying to convince the unvaccinated people I know and love that the vaccines are safe and effective and the best bets that we have right now of helping prevent serious illness and complications from COVID-19.

I recently talked with Dr. Ala Stanford, founder of the Black Doctors COVID-19 Consortium, about the anti-vax holdouts, and what she said was sobering.

“Everyone you’re not going to reach,” Stanford told me. “I pray for those who decide that they are not going to get it, that the course they have is not horrible.”

In the end, she said, it’s going to be a survival of the fittest. By that Stanford didn’t mean just of the physically fit but also of those who are the most mentally fit.

She pointed out, “Those who are easily swayed or who believe myths, conspiracy theories, and information that is not fact-based, they may or may not make it.”