‘Vaccines are not enough’: A COVID-19 expert on the measures people need to take to slow the spread

DENVER — An expert in COVID-19 transmission from Colorado says the state needs to do more than mandate vaccines to stop the current surge of the fifth wave of the coronavirus pandemic as cases and hospitalizations continue to reach levels which could soon overwhelm the state's hospital capacity.

Dr. Alex Huffman, an associate professor of chemistry and aerosol science at the University of Denver with nearly 20 years of experience who has been studying how aerosols are transmitted through respiratory sources since the pandemic started, told Denver7 Monday that while vaccines are a really important strategy in fighting the pandemic, they are not enough at this point to curb the spread of the disease — especially as Coloradans make plans to travel for the holidays.

Denver7 spoke with Huffman about the state's recent move to mandate vaccines for large, unseated public indoor events and what else needs to be done — both by state health officials and on a personal level — to curb the spread of the disease.

This interview has been edited and condensed for clarity.

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Given what you know about COVID-19 transmission and your years of expertise studying how airborne viruses spread, is requiring a COVID-19 vaccine at large indoor events the right approach by the state to curb transmission, or is something else besides vaccines needed to really stop the spread that we're currently seeing in Colorado?

There's no question that getting a vaccination and increasing the percentage of people in the state that are vaccinated is a really, really important piece of the puzzle, but we can't vaccinate our way out of the pandemic. There have to be other things that we put into place — especially right now when the transmission is so high in the state. So, having as many people put on high-quality tight-fitting masks as much as possible is important, reducing the number of people that are gathered together in indoor spaces, increasing the ventilation and filtration in those places — those are really important pieces as well. Vaccines are great but it can't be the only solution we put into place and we've got to stop the transmission with these other strategies as well.

So what you're telling me is that a vaccine-only approach, as the state is doing, is simply not enough to curb the spread of COVID-19?

Absolutely. The vaccine is really important, but vaccines by themselves are not enough. We as a community need to put other mitigation steps in place and we've got to work together to slow this spread that's just going like wildfire through Colorado right now.

Any advice or concerns going into the holiday season for people wanting to enjoy the holidays as safely as possible?

Right now in Colorado and many other places, the rate of transmission is high and the number of people in hospitals is really high and we're running out of ICU beds, and so we need to take the transmission of COVID from person-to-person seriously, and we need to do what we can to help it not keep going from person-to-person.

That means putting some precautions in place, reducing the number of people that you have at your holiday meal, cracking the windows a little bit to get some airflow, putting a HEPA filter in place, putting on masks when you can when you're not eating, if possible — even move your meal outside. Some of these things can make a big difference in terms of reducing the spread between people at a party.

What mitigation efforts do you think are needed right now in Colorado to curb the spread of this disease?

With the rate of transmission so high in Colorado, we really need to be even more serious about wearing good quality masks when we're together indoors, especially when there are a lot of people in a smaller place, and so I encourage people to put on their masks whenever they're out in public or with people indoors. Masks are still really, really important to this puzzle and I would love to see a bit more stringent regulations on masks right now, potentially a statewide mask mandate. I know that this is a politically contentious issue and it gets into all sorts of other things that wrap together, but we as a community need to be masking more, however that happens.

Another piece of the puzzle is, we really need to pay attention to indoor ventilation by putting some HEPA filters in place in school rooms and lunch rooms and wherever people take their masks off. Those settings are a particularly dangerous place to be and so we've got to focus on cleaning the viral particles out of the air so that other people don't breathe them in. Whenever we're together with people indoors, it's important to open the windows, add some filtration and ventilation, and honestly, be outside whenever possible, especially with Thanksgiving coming up. If there's any way that you can move your meal outside, that would be great. If you can spend some of your mingling time outside and come in later, that would be great too.

However we can reduce the amount of time we spend together indoors with people that we don't normally live with will help quite a bit. Most of those things can't be mandated but they're best practices in terms of how we can actually slow the spread.

What concerns do you have going into the holiday season. Is there a message that's not going out to the public — especially now during the holidays — about transmission that you would like to see?

In terms of going into Thanksgiving, yeah, I have lots of concerns. It's a different situation than it was last year when very few people were vaccinated, but this year there's more vaccination in the state; however, there are still plenty of people who are unvaccinated — everyone under 5 and even children 5-11 who have had the vaccine, the vaccine is not going to have time to fully provide immunity by the time Thanksgiving comes around.

For the people that are fully vaccinated, there are certainly breakthrough cases where even if you're fully vaccinated, you can be infected and pass that on to people even if you don't have as much likelihood of being hospitalized yourself. So with Thanksgiving coming and so many cases in Colorado, we've got to take this seriously again this year, and so I would encourage people to reduce the number of people that they have inside when they have their meal together, add filtration inside with a HEPA filter or a do-it-yourself filter, add masks and keep them on as long as you can do that in the biggest space you can, open your windows, treat the airborne spread of this disease seriously right now.

Actually, I wrote a thread about that last night. I wrote a thread putting together just my thoughts on both gathering some recent articles that people put together, but also saying, 'Okay, this is my summary of some of the things that you need to keep in mind' just as I try to remind people, because I don't think there's been enough attention right now as to the risks associated with Thanksgiving.

In particular, Thanksgiving, or holiday meals of any kind — really, meals of any kind when we eat indoors — are potentially high-risk situations because we take off our masks. We sit together, we sit close to each other, take off our masks, and especially at a holiday meal when people gather who haven't seen each other in a long time and maybe you're drinking alcohol, people get a little louder, and that's great. But whenever you're louder, more aerosols, more virus comes out of your mouth and so the risks just skyrockets when you're together in these situations, and so we've got to take this seriously.

Even though many more people are vaccinated this year, we still need to take the COVID pandemic seriously and do what we can to reduce the spread from person-to-person, especially people who are not vaccinated or immunocompromised. And so the principles are still the same as they were last year: Masks, ventilation and filtration, being outside when possible, and it's important to pay attention to some of these things. Or even just consider not gathering together, especially if there are any unvaccinated people among you. We just can't treat the pandemic as being over yet. We have to treat it seriously.

Many people who are vaccinated will gather for Thanksgiving and the other holidays coming up. What's something the public should understand about the current state of the pandemic in Colorado?

I think that with Thanksgiving coming up, what I'd like people to understand is that the COVID pandemic isn't over, that there are transmissions that are still taking place, especially in the unvaccinated population, and anyone who has not yet vaccinated — whether adult or child — needs to be especially careful and really considered not meeting with one another, and so I'd like to see that come into the conversation a bit.

But even among people who are vaccinated, there is still the potential to be a silent spreader, to not have symptoms, but then share that with people who are not vaccinated or can be at risk, and so I'd like to see us make sure to get the message out to enjoy the holiday in the safest possible way. In some cases, that may mean gathering together and with protections in place; in other cases, that may mean just not gathering with people if you're unvaccinated and not taking the proper precautions.

I'd also like to see the discussion that the proper precautions are what they have been from almost Day One: Good masks, ventilation, HEPA filtration in rooms, open up the windows and limit the number of people in there and the time that you spend there. Those things will help tremendously as we add these layers together to prevent onward transmission. We just can't treat the pandemic as being over yet. We have to treat it seriously.

Can you give us an idea of what type of masks better protect the public? There's cloth masks, there are surgical masks, there's N95/KN95s. Could you briefly touch on what kind of masks people should be looking into buying and wearing if they want to celebrate the holidays and beyond safely?

Masks do a great job of preventing aerosol from coming out of your mouth or being breathed in from other people, and so the tighter the fit of the mask, the more it prevents the aerosol from leaking around the outsides of that and being breathed out or in.

Surgical masks are great at filtration but don't fit very well to your face and so don't provide great aerosol transmission prevention. They do a much better job than nothing, but I would really recommend people — at this point — to be wearing the best quality and the best fitting mask they can.

I have worn an N95 mask exclusively for months and so you can buy these at a variety of box stores locally. You can also buy them online. One of my favorite places is Project N95, a nonprofit organization that vets their masks and the sources they come from to make sure that they're both inexpensive and high quality.

No matter what it is that you're doing, I suggest putting on a mask that is of high filtration quality like an N95 with a NIOSH stamp. KN95 can be good, KF94-rated masks are excellent. But whatever it is, make sure that it seals tightly to your face so that the air doesn't leak around the outside and then go into the room without being filtered.

What about beards and using a KN95 or N95 mask? Last year, there was some sort of graphic going around saying something along the lines of, “Shave your beards” and a lot of people in Colorado have beards. Is it safe to wear an N95 mask with a beard or should people start thinking about removing them? What's your advice on that?

Well, I'm not going to say whether you should shave your beard or not. But I can tell you the scientific principle which is that, if the mask is not sealed well to the skin of your face, air is going to leak past it and so there's nothing you can really do about the fact that if you have a beard, especially the bigger and the bushier it is and the less the mask seals to your face, the more air is gonna escape around it. So if you have a big beard, the mask is just less efficient, there's not much we can do about that.

Earlier we were talking about some sort of mitigation efforts around the holidays. Say I'm having a party with ten people and we're going to drink a little. What are some best practices — not just for the holidays — but for gatherings overall, when it comes to preventing the spread of COVID-19?

Whenever people gather together and eat together indoors, that's when you take your mask off and you may drink a little bit and you get extra loud and you breathe out and you have even more aerosols coming out of your mouth, so we've got to put as many layers of protection as possible in place.

Obviously, if you are not vaccinated, get vaccinated as soon as you can. Right now it's too close to the holiday time to be fully protected even if you are getting it (the vaccine) right now. One thing that you can do is to add some rapid COVID-19 tests if you're gathering together. Have everybody that morning take a rapid test that you can get from a local pharmacy, it takes 10 minutes and it gives you some confidence that somebody is not in the room that has the sickness and no symptoms. Everybody should wear high-quality, tight-fitting masks whenever they're not eating, if possible. Eat outdoors if you can, and mingle outdoors before you come in. Add some ventilation by opening windows. Add a HEPA filter or Do-It-Yourself filter in the space. Add a little bit of distance when you're together inside, make the smallest group you can inside, do that in the biggest volume (of room) that you can because then that dilutes the aerosol. And, if possible, when people have their masks off, especially reduce the volume of the music so you're not having to shout over it, that reduces the amount of aerosol that's coming out of your mouth.

Is gathering outside in large groups and close together counterintuitive?

If you could have your gathering outside, then that makes the risk quite a bit less because the air and the aerosol doesn't build up in the room and make high concentrations over time, so moving outside can be great. But even if you're outside, you want to add a little bit of distance between yourselves, if possible, because you can still breathe the air that somebody else is breathing out whether you're outside or inside.

Think of a smoking situation where someone is smoking near you. If they're on the other side of the room inside, that smoke builds up so that you will eventually smell it and it'll be in high concentration. Now if you move outside, it doesn't build up in concentration because the natural ventilation whisks it away. But if you're standing two feet from someone, that smoker is going to breathe in your face and you have a big plume of smoke or of aerosol that's coming out of their mouth, and so even outside you want to add a few extra feet so as to not be in that direct breathing zone of the person breathing out. But! It's important to note that outside is almost always dramatically less risky than indoor spaces because the air just doesn't build up outside.

What about carbon dioxide monitors? Should those be added to a person's toolbox to prevent spread, as well as HEPA filters? What could you say about those things as well as you know, proper ventilation and all those things?

So the goal is to reduce the concentration of aerosols that build up in indoor space. So, ventilation by opening windows can be a great way to do that. Adding HEPA filtration or a do-it-yourself Corsi-Rosenthal Box filter is a great way to remove the aerosol from the room, so that helps clean the air. One way to figure out how much air from people breathing out is building up in the room is to use a carbon dioxide monitor, where when you breathe out, you breathe out carbon dioxide or CO2, but you also breathe out aerosols and those respiratory aerosols are what we care about.

We can't measure those very easily in an indoor space but we can measure carbon dioxide pretty easily, and so if the concentration of CO2 starts to go up much above 800 parts per million (ppm), then it means that the air that people are breathing out is building up and there's a high concentration in the space you're in. So, a CO2 monitor like this that can be purchased for about $200 can be one really nice tool in your toolbox to get an idea for how good the air quality is in the indoor space. It's important to keep in mind that this doesn't do any cleaning, it's just a window into how well-matched the ventilation is to the number of people in the room. But for the people that have access to spending something like $200 on a CO2 sensor, it can be a really nice thing to bring with you. I have several of them and I honestly bring them to lots of places with me to get an idea of how good the air quality is in that indoor space.

What kind of messaging needs to be happening right now for the public to be really informed about how dangerous the situation is at this time? Is there something that either politicians or the media aren't telling people that they should be telling them to really give them the information they need to better protect themselves as this current surge of the coronavirus pandemic is happening here in Colorado?

I would say that the emphasis should still remain on the fact that the pandemic isn't over and is continuing in Colorado and in many places. As you've seen, the hospitalizations are high, the ICU cases are high and it is still possible as a person who has been fully vaccinated, to be a carrier of the virus and then spread that on to other people, especially to people who are not yet fully vaccinated. We have to work together to put some preventative measures in place that are not only reliant on the vaccine. We need to wear masks. We need to be aware of ventilation and filtration in shared spaces and in schools, so as to be able to help the portions of the community that are not yet vaccinated and to help prevent the onward transmission, even among vaccinated people.