Dr. Miller Examines Masks in the Age of Omicron

Is a discussion of masks needed at this point in the pandemic?  I think so for two reasons.  First, unlike two years ago, there are now a huge number of different masks on sale from an even bigger number of manufacturers.  How can you tell the difference and decide which one to buy?  Second, while we all hope that this pandemic will start to show a decline over 2022, Omicron has presented a challenge that makes one’s choice of mask more important than before.

The Omicron challenge.   While Omicron appears to be less virulent with a lower rate of serious illness and death, this is offset by its tenfold increase in transmission rates.  This means that while a lower percentage of people with Omicron may end up in the hospital, the total number of people getting infected is also higher than before.  Why is Omicron more contagious?  The answer rests with the spike protein on the surface of all coronaviruses.  The spike protein is the key that fits into the lock on the surface of a host cell allowing the virus entry.  This lock is known as a receptor and in normal life functions to allow messengers, like hormones, to enter the cell.  Viruses take advantage of these receptors to fool the cell into giving them entry. The better the key fits, the more likely the cell will open the door and thus become infected.

Here is the important part.  A better fitting key means less virus particles need to be inhaled to get a solid infection going. In other words, the result of a better spike-receptor match is increased contagion.

The virus has not developed new ways of floating through the air; it is still primarily spread by respiratory droplets.  However, because the Omicron variant can lead to more infection than before, it is important that our masks be even better at filtering out the virus.

Masks versus respirators.  A respirator is simply a mask that has been certified by the National Institute of Occupational Safety and Health (NIOSH) to protect the wearer from inhaling potentially dangerous particles.  In order for it to do this, respirators must make a tighter fit around the face than a mask and are generally thicker, being made of multiple different layers each with different filtering properties.  A key component of respirator manufacture is one or more special layers of polypropylene fabric that are given an electrostatic charge to attract and trap even very small particles which might otherwise pass through.  Another requirement is that they must have headbands and not ear loops. This is to reduce the risk of the respirator being knocked off or accidentally dislodged.

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Medical grade paper masks are loose fitting and thinner and were primarily designed to trap respiratory droplets from escaping the wearer and entering into a patient’s wound, such as during surgery.  As such, they are highly effective in controlling the spread of infections from wearer to patient, which is why they are used extensively in surgery.  However, they offer less protection in the other direction.  They are not made with the special electrostatic fibers so, along with their relatively loose fit, will not trap small particles or aerosols. 

Cloth masks and gators generally provide even less protection than a medical grade mask and are not advised at this time.

What do the numbers and letters mean?  The number specifies the percentage of particles it must be capable of filtering out.  An N95 respirator must filter out at least 95% of large and small particles down to the aerosol size.  N95 respirators are not designed to filter out gases or vapors.  While they must filter out small aerosols, they do not resist oil-based aerosols and the “N” designation stands for “non-oil” indicating that the respirator does not protect against oil aerosols.  “R” designates oil resistance and “P” designates oil proof, however, neither of these two types are relevant when we talk about viruses.  There are also N99 and N100 respirators, but these are for special applications when using highly dangerous compounds and are usually part of a face covering shield.  This designation system was created by NIOSH and is used in America.  In the European Union, the FFP2 is an equivalent designation to the N95.  In China and most Asian countries, the equivalent designation is KN95 or in Korea KF94 for “Korean Filter”.  The KN95 does not require the head strap and thus can be found with ear loops which are far more comfortable.

The respirator advantage.   Once again, the key elements that make the N95 superior to a simple medical grade face mask are the special layered materials used to make it and the tighter fit around the nose and mouth.  This level of filtering is simply not provided by the medical grade mask.  Since the infectious dose with Omicron is so much lower than with previous variants, having that extra filtering capability is important.  The downside to respirators is that, since they are thicker it is sometimes more difficult to breath through and since they require a tighter fit, then they are definitely more uncomfortable. 

Finding a reasonable balance.  My recommendation is to first find masks that are built well enough not to fall apart and are reasonably comfortable to wear.  They should fit as snuggly around the mouth and nose as possible without causing pain especially over the bridge of the nose.  I continue to wear a medical grade mask when simply out in public such as at the grocery store, but if I will be in a more enclosed space with a large number of people, for example, flying in an airplane, then I use an N95 or KN95 respirator.  This is especially important if a lot of folks around you are not wearing masks.  I recommend avoiding cloth masks all together, but a cloth mask is better than going without a mask as it will reduce the escape of respiratory droplets that the wearer is producing.