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A deeper look at our understanding of COVID vaccines and transmission

Because of the novelty of COVID-19 and the vaccines preventing it, the data is incomplete. As experts get new information, they provide new guidance.

DENVER — The excitement around getting vaccinated against COVID-19 has to do with what life looks like afterward. 

As experts' understanding of COVID evolves, there, too, has been an evolution in our understanding of what is safe and what is not.

Dr. Michelle Barron with UCHealth and Dr. John Hammer with HealthOne, both infectious disease specialists, helped us understand where we are now, a year into the pandemic.

What studies have been done? 

Both doctors said studies are being done on all three vaccines offered in the United States -- from Moderna, Pfizer and Johnson & Johnson -- to study transmission after people are vaccinated. 

The tests were done in labs and also by tracking whether people who are vaccinated infected other people near them. Those studies so far are finding that the risk of someone fully vaccinated spreading COVID was low. 

The data and the research, however, are preliminary and incomplete, which means there is a lot still to learn about transmissions after vaccination and its impact on the pandemic. 

"Data is emerging demonstrating that fully vaccinated people are less likely to have asymptomatic infection and therefore potentially less likely to transmit the virus to others around them," Hammer wrote to 9NEWS. "Studies are ongoing that will hopefully confirm the extent to which this added benefit from vaccination will help to slow the pandemic."

Barron added the idea is that a person who is fully vaccinated wouldn't be able to build up enough of a viral load to transmit the virus to someone else.

"That still leaves the question though -- that's the laboratory version, but how does it perform in real life? And that's where I think we still don't have enough numbers," she said.

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How did these studies contribute to the CDC guidelines?

Barron said the studies, along with a general understanding of how vaccines work, have contributed to the Centers for Disease Control and Prevention (CDC) updating their guidelines.

"A little bit of both," said Barron. "People shouldn't be surprised things changed."

Barron added that decisions are being made as experts are gaining more understanding about the virus.

The CDC guidelines now say you can gather indoors with fully vaccinated people without wearing a mask. People are also allowed to gather indoors with unvaccinated people from one other household, unless they are people or live with someone at an increased risk for severe illness from COVID. 

But people, regardless if they are vaccinated or not, need to continue their COVID protocols and precautions in public spaces, gathering with unvaccinated people from more than one other household or seeing someone who is not vaccinated at an increased risk of severe illness or death from COVID, or lives with someone at an increased risk. 

It's also important to avoid crowds. 

For a more detailed explanation, check out the CDC's interim guidelines on their website.

What about variants?

The CDC said they're still learning how effective the vaccines are against the COVID variants, but arly data shows the vaccines may work against some of them but could be less effective against others. 

Both doctors we talked to agree. 

Barron said the idea is that if you are vaccinated and contract a variant strain of COVIDm you would likely fall less sick. Along with that, researchers are also looking more into the transmission from a vaccinated individual if they have the variant strain. 

"To date, at least one variant (the B.1.351 variant first described in South Africa - but not necessarily from there) has shown some ability to partially evade the vaccine-induced immune response in the lab.  The immune response, however, was still thought to be adequate to protect vaccinated people.  Additionally, some vaccines have been somewhat less effective in trials where this variant was circulating. Fortunately, studies of new vaccines using existing platforms, but targeting the worrisome new variants, are already underway," Hammer said.

Both doctors reminded people that the vaccines aren't 100% guarantees, so people need to do risk assessments. 

To be "fully vaccinated" means it's been at least two weeks after your second dose of the Moderna or Pfizer vaccine, or at least two weeks after receiving the Johnson and Johnson vaccine. 

RELATED: VERIFY: What do the CDC's updated COVID guidelines for fully vaccinated people say?

The Colorado Dept. of Public Health and Enviroment (CDPHE) provided this statement: 

"We recommend that all people who are able to be vaccinated get their vaccine once they are eligible.

Some variants appear to spread more easily and quickly than more common strains that cause COVID-19. If a variant that spreads more easily becomes the dominant COVID-19 virus in our state, we could see cases spread within our communities at a faster rate than in the past, which could lead to another strain on our health care system.

The most effective ways to prevent the spread of any COVID-19 virus remain the same: wearing a mask in public, maintaining at least 6 feet of physical distance from others, limiting contact with anyone outside your household, washing your hands often, staying home when you are sick, and getting vaccinated when it is your turn.

Scientists are still learning how effective the vaccines are against new variants of the virus that causes COVID-19. Early data show that while vaccines are still effective, they could be less effective against some variants. We are learning more each day about the characteristics of new variants. That said, early data also suggest minimal impact on vaccine effectiveness with B.1.1.7, the UK variant that is one of the more common variants in the U.S. and Colorado right now. CDC will share updates as soon as they are available.

Dr. Rachel Herlihy provided a variant update yesterday during Governor Polis’s press conference. You can watch the press conference and view the presentation at https://www.colorado.gov/governor/news/4536-governor-polis-provides-update-covid-19-response.

About Virus Variants: 

Viruses constantly change through mutation, and new variants of a virus typically appear over time. Sometimes new variants emerge and then disappear. Other times, new variants emerge and continue to spread. Scientists have documented multiple variants of the virus that causes COVID-19 globally during the pandemic. Scientists are studying these variants to learn more and to control their spread. More information about variants can be found on the CDC’s website."

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