MEDICAL MONDAY: Latest CDC Guidelines

CBSN Bay Area interviews Stanford Health Care's Dr. Neha Narula about the latest CDC guidelines when it comes to facemasks and 'breakthrough' cases of COVID-19.

Video Transcript

NEHA NARULA: Yes. Just in time for summer, we heard the CDC update their guidelines on asking masking for unvaccinated versus vaccinated individuals. And these updates really do highlight the success of the vaccines. And they're an enthusiastic reminder of life heading back to some sort of normalcy.

But I do want to emphasize to our viewers that when it comes to unvaccinated individuals, as well as both groups, in indoor settings as well as large outdoor gatherings with packed rallies, stadiums, or even concerts, precautions do still apply. We know that in the outdoor setting, the airflow is much more natural. And that prevents virus from accumulating in the air. But how much safer is it?

So data is coming out. And we've been studying this for the past year. There was a meta analysis recently published in the Journal of Infectious Diseases that actually found that the spread of coronavirus is 19 times more in an indoor setting compared to an outdoor setting. And in addition to this, we actually have data coming from Ireland that investigated about 232,000 COVID cases. And we found that only in about one out of every 1,000 cases was the transmission traced back to an outdoor setting.

So again, the risk of catching the virus outdoors is quite small. And with summer around the corner, with these updated guidelines I'm hopeful that this will serve as an incentive for those that have previously been on the fence about the vaccine to go ahead and get it so that we can move past this pandemic once we have a good number of people that have been vaccinated.

- But say you passed somebody going on a hike who maybe is running and is breathing kind of hard. What is the risk of transmission if you pass by someone like that?

NEHA NARULA: So certainly when passing someone who is exercising for a brief instance of a few seconds or a couple of minutes even, the risk of catching the virus is minuscule. Like we talked about earlier, the outdoor airflow is what really helps us.

But what I want viewers to take away is that timing is important. A few seconds, not a problem. But if you are planning on being around someone for 10 to 15 minutes while they're exercising, huffing and puffing, or even coughing, that certainly will raise the risk of contracting it if they are infected. And this particular scenario is a great reminder why the CDC provided specific examples so we can kind of take those examples and use them on an everyday, more of a realistic basis.

They also emphasize that you need to take into account your own personal risk, the level of spread of the virus within your own community, and the number of people involved in the particular activity you're going to be partaking in. While we're doing better as a nation, we're still not at herd immunity levels. And there are communities where vaccine rates are quite low.

So we still have to practice all of the precautions and use a general sense of what is low risk, what is high risk, to estimate your own individual risk when it comes to contracting the virus. But as for running, jogging, hiking outdoors, you'll be OK if you pass by someone that's breathing hard for a couple of seconds to a few minutes or so.

- And as more people are getting vaccinated here in California, we're starting to hear a few more cases of what's being called breakthrough cases where people who are fully vaccinated are still getting infected. I think California has more than 1,000 of them at this point. Is that something to be concerned about?

NEHA NARULA: These vaccines, while incredibly effective at preventing severe disease and hospitalizations, are not perfect. We know that. So naturally, we did expect to see some breakthrough cases. But it's important to take everything into context. In California between January 1 and April 21 of this year, recent data released has found 1,379 patients that were fully vaccinated ended up contracting the virus.

So now we know that about 30% of Californians are now vaccinated. And that puts us at a rough number of 11 to 12 million vaccinated individuals. So when you take into account that almost 1,400 cases, it's a very small percentage of the vaccinated individuals. It's actually less than 0.01%.

Additionally, if you take it a step further, we've had a total of 1.4 million COVID infections in that same time period within California. And so taking the caseload from vaccinated individuals, again, less than 0.1% when you look at the numbers. They're small.

I've said it before. I'll say it again. Vaccines are still our best chance at avoiding COVID-19. We still are waiting for the full data on the severity of infection in vaccinated individuals and mortality rates. But we do know that it is a small percentage. And looking at these cases further will help us understand the virus better, the vaccines better, and will continue to guide us on the precautions that we may need to continue to take in the future.

- And one thing that I was curious about is people who are fully vaccinated and they do get infected, do they still carry a large viral load? Is that possible?

NEHA NARULA: When it comes to vaccines, there's always a lot of confusion and understanding of what the end goal is. Most people consider the goal of vaccines is to ultimately prevent infection when in actuality most vaccines actually prevent disease, not necessarily infection. And as we were discussing, we've seen these breakthrough cases. And the question now is, I've been fully vaccinated. What if I get this virus? How likely am I to give it to my family members, to give it to my kids who aren't yet vaccinated or can't be vaccinated?

And we now have data from Israel where there was an extremely successful national vaccine campaign. And they are showing that the Pfizer-BioNTech vaccine and just vaccines in general substantially reduce the total number of viruses within the body. And this is known as the viral load. And they found that the viral loads in the small number of infected individuals that have been vaccinated was reduced to four times less than in a unvaccinated individual.

And when we correlate that to how likely we are to transmit, we know that viral loads are a key driver in the transmission of infection. So these findings are actually fantastic. They indicate that the vaccines can help lower the risk of transmitting to a specific group of people or individuals that may be around if you do contract the virus after being vaccinated.

So ultimately, bottom line is we are headed in a good direction. And we can thank our vaccines for that. They block you from getting severe disease, but now we're also being shown that they also reduce passing the infection on to others in case you are one of the few that do end up getting the vaccine. So if you haven't already, talk to your doctor. Clarify any questions you may have. And go get that vaccine to protect yourself and your loved ones.