Even as a growing body of evidence confirms the effectiveness and protective strength of COVID-19 vaccinations, experts advise it’s prudent to greet every bit of good news with a measure of caution.

The U.S. Centers for Disease Control and Prevention this week released results of a real-world study showing the Pfizer and Moderna vaccines prevent both symptomatic and asymptomatic people from causing new infections.

That implies fully vaccinated people not only are protected from COVID-19 themselves, but won’t infect others. Fear of people without symptoms infecting others is the foundation of many government-imposed restrictions on civic and commercial life, including social distancing, face coverings and orders closing businesses and limiting gatherings.

The study at least raises a question about whether those practices need to continue among vaccinated people and how long they need to continue after most people who want to be vaccinated have been.

The study was notable in several ways, said Alan Barrett, director of the Sealy Institute for Vaccine Sciences at the University of Texas Medical Branch.

In their haste to get FDA approval for emergency vaccine use, drug makers didn’t study how effective their serums were at stopping spread of the virus, only how well they worked at preventing serious illness.

The new study tracked 3,950 health care workers in six states after they were vaccinated. It found the vaccine might not just prevent symptoms, but stopped people from being infected entirely. Vaccinated people were tested for COVID-19, even if they didn’t have symptoms, and were found to be infected at a lower rate than an unvaccinated control group.

The result can help explain dropping infection rates in places where vaccinations are increasing, Barrett said. It’s another reason people should seek vaccination, he said.

“It suggests that if you have somebody who’s had the vaccine, they can be next to somebody and not infect them,” Barrett said.

But there’s also reason to take the good news with caution, Barrett said. The study group was relatively small and spanned only a three-month period, he said.

There’s also a chance vaccines available now won’t hold up against variants of the virus as they continue to emerge and spread around the world.

“It’s a relatively small window if you’re trying to make big conclusions,” Barrett said. “It’s a relatively small number of people. I’m sorry to be negative. You’re not taking a very big cross-section of the whole country, but it’s the best you can do at the moment.”

Those limits might mean it will be some time before health officials stop making the same public health recommendations they’ve been making for more than a year.

Dr. Philip Keiser, Galveston County’s local health authority, said it would likely be mid-summer before he would be comfortable recommending that people stop wearing masks in certain situations.

“I think we’re going to be with that one for a while,” Keiser said. “Masking has really been the one intervention that we’ve done that has been the most effective and has given us the most bang for the buck.”

If new infections continue to drop, it’s possible health officials could advocate different strategies that aren’t possible when there’s community spread of the virus, Keiser said. Those include identifying infected and exposed people and quarantining them quickly, Keiser said. Until then, community-wide precautions likely will remain as public health recommendations.

All that caution aside, the past week has been filled with positive news about COVID vaccinations. Studies have begun to show that vaccines are effective at protecting people as young as 12, setting up the possibility that younger people could be on their way to joining the list of the vaccine-eligible people.

On Thursday, Pfizer and BioNTech reported their vaccine still was highly effective six months after initial vaccinations, a finding that hints that people might not need frequent booster shots to maintain their resistance to the virus.

And on Friday, the CDC announced, based on current data, the agency believed travel represented a low risk to vaccinated people.

At a press conference announcing that finding, however, CDC Director Rochelle Walensky also showed how reluctant officials are to change their recommendations.

“While we believe that fully vaccinated people can travel at low risk to themselves, CDC is not recommending travel at this time due to the rising number of cases,” Walensky said.

“With so many people still unvaccinated, it is important that everyone — regardless of vaccination status — continue to take prevention measures in public.”

John Wayne Ferguson: 409-683-5226; or on Twitter @johnwferguson.

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