With the federal mask mandate for airplanes, airports and public transport abruptly ending last week, the question of “is one-way masking effective?” arises. One-way masking is when one individual is masked yet others are not. Many may find themselves in this situation while the justice department appeals the decision. While the data is clear that masking is most effective when everyone partakes (as discussed in my previous post), there is still some benefit to masking even if those around you are not masked. The degree of effectiveness however depends on what kind of mask the wearer is wearing, the ventilation and air filtration in the space being occupied, physical distancing, the community transmission levels in the area one is traveling from or traveling to, duration of exposure etc.

I previously discussed the best masks to protect against highly transmissible variants such as omicron, which are also the best masks to wear if those around you are not masked. NIOSH-certified N95 masks are still the most effective, but the masks discussed here including KF94s and KN95s are great alternatives if one is unable to get an NIOSH-certified N95. Earlier this year a study showed that consistent use of a face mask indoors was associated with lower chance of becoming infected with SAR-COV2 and respirators with the highest filtration capacity offered the most protection. The details of this study were discussed in my previous post.

Studies have shown that wearing an N95, KN95 or KF94 can reduce risk of transmission to 1% over one hour of exposure if everyone is wearing one, but there is still benefit to wearing one even if others are not. If you are the only one masking and you opt to wear a well-fitted N95, risk of transmission from someone who is infected and unmasked is decreased to 20% over the course of a one hour exposure. This same study found that if the masked person is wearing a surgical mask however, there is a 90% risk of being infected after 30 minutes of being 5 feet apart. The evidence is again clear that the type of mask and the fit of the mask matters.

Despite the recent ruling ending the mandate, I hope to see the majority of people continuing to mask on planes/public transportation and other crowded areas. I know I will continue to mask to protect the most vulnerable including children who cannot be vaccinated (anyone under age 5) and immunocompromised individuals who don’t receive the full benefit of protection from vaccination alone. Other things to consider are masking will prevent travel disruptions due to getting sick, decrease staff shortages on flights and other modes of transportation (we are already seeing more flight cancellations due to COVID-19 in employees), and will further protect YOU.

Andrejko KL, Pry JM, Myers JF, et al. Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021. MMWR Morb Mortal Wkly Rep 2022;71:212–216. DOI: http://dx.doi.org/10.15585/mmwr.mm7106e1external icon.

Bagheri G, Thiede B, Hejazi B, et al. An upper bound on one-to-one exposure to infectious human respiratory particles. PNAS. 118(49). December 2, 2021. https://doi.org/10.1073/pnas.2110117118

Brosseau LM. Fit testing respirators for public health medical emergencies. J Occup Environ Hyg 2010 Sep 30;7(11):628-32

Lindsley WG, Blachere FM, Beezhold DH, et al. A comparison of performance metrics for cloth masks as source control devices for simulated cough and exhalation aerosols. Aerosol Sci Technol 2021 Oct 3;55(10):1125-42

With many people relying on at home rapid antigen tests to be able to safely gather with family members and attend events, it’s important to know just how far these tests go at helping us assess risk. There is a range of variability in the sensitivities of these rapid home tests especially when it comes to the omicron variant. Sensitivity refers to the ability of a test to accurately give a positive result in someone who is infected with the virus. Numbers for these rapid antigen tests have ranged with some studies showing sensitivity as low as 44% in asymptomatic individuals and an overall sensitivity of 65% and others showing sensitivity of roughly 92% in symptomatic individuals and 78% in asymptomatic individuals. The accuracy of these tests as discussed in the studies does depend on whether one is symptomatic or not (with symptomatic being more accurate) and of course at what point in the course of the illness one is being tested. That being said, there is some utility to rapid antigen tests.

A rapid antigen test detects a protein on one of the spikes of the coronavirus and is less sensitive overall than a PCR test because it takes more viral particles for it to reveal a positive result. A rapid antigen test may be best used if one is trying to determine if still infectious and a risk to others. It is unclear at this point how much viral load one needs to carry in order to be considered infectious, but if the rapid antigen test is positive, the result should be trusted. The timing of when to take the test is important though since you may not have a high enough amount of virus to be detected if you test too early after exposure (which is why PCR would be better early on) so if asymptomatic after a known exposure, testing with a rapid antigen test around day 3-5 and again at day 5-7 since exposure would be more accurate.

A PCR test also known as a reverse transcription-polymerase chain reaction test can pick up small amounts of viral genetic material. The test then amplifies the genetic material, making it a very sensitive test. However, because it reveals positivity even when there’s a small amount of virus, it can actually stay positive for many weeks after one is infected even if one may no longer be “infectious.” An appropriate time to take a PCR test is when one has had a known exposure to someone with COVID-19 or is experiencing symptoms. Since initial studies suggested that the 1-2 days before symptom onset and 2-3 days after symptom onset may be when one is the most infectious, it is important to opt for a PCR test because it may detect the virus earlier than a rapid antigen test, which is not as sensitive. That being said, a recent Japanese study found that viral loads for omicron were highest at days 3-6 after symptom onset, which also calls into question the shortened quarantine guidelines put out by the CDC.

Of course, it’s important to recognize that access to affordable testing is a major obstacle for many. This is why we need to ensure that everyone has access to free testing and delivery of these tests is equitable. For more information about specific rapid tests and their sensitivity, refer to the links below.

https://pubmed.ncbi.nlm.nih.gov/34242764/

https://www.cdc.gov/mmwr/volumes/70/wr/mm7003e3.htm

https://www.nytimes.com/article/at-home-covid-tests-accuracy.html?ref=oembed

https://www.health.harvard.edu/diseases-and-conditions/if-youve-been-exposed-to-the-coronavirus

https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2783099

https://www.niid.go.jp/niid/en/2019-ncov-e/10884-covid19-66-en.html

It has become increasingly important to upgrade our masks given how contagious the omciron variant is and the recent data suggesting the need to switch to high filtration masks, but which masks are worth investing in? The two most important features we look at our mask quality and mask fit. Studies have shown that the risk of infection increases within minutes for someone who is wearing a cloth or surgical mask compared to someone wearing a well fitted, high filtration mask where exposure would take hours before it became a threat. Of course, fit-tested National Institute for Occupational Safety and Health (NIOSH) approved N95 masks often used by healthcare workers offer the best protection overall, but even non-fit tested N95 masks offer more protection than any other mask. In a study by Lindsley et al. 2021, % outward and inward leakage was evaluated and time to infectious dose for an uninfected person was assessed with different types of masks. It was demonstrated that the N95 is superior to surgical masks, cloth masks and wearing no mask at all. Brosseau et al. 2020 assessed non-fit tested N95s and also arrived at favorable conclusions. For those who may not have access to N95s, KN95s and KF94s offer excellent protection. For specific mask recommendations, check out the mask nerd, Aaron Collins. As an engineer and expert in aerosol science, he does his own experiments looking at filtration efficiency (FE) of various masks and has great videos on youtube with detailed reviews (keep in mind experiments are done on his own face). I took a look at these and put together his top rated masks:

Bluna FaceFit Large KF94 with 99.1% FE

Mask Lab KF Style FFP2 with 98.3% FE

CleanTop Evergreen KF94 with 99.8% FE

LG Airwasher KF94 with 99.1% FE

For smaller faces, mask nerd recommends the BOTN Medium KF94 with 99.7% FE and Dr.Puri Medium KF94 with 98.7% FE

Powecom Black KN95 with 96.8%-98.9% FE

Arun External Nose Clip KN95 with 99.8% FE

With children going back to in person learning all over the country, many parents are wondering what masks are best to help keep their kids safe. @masknerd has a great youtube video that provides some guidance, but I would also add that the best mask for your children is the one they can keep on the longest. Here are the ones recommended by @masknerd:

Blue Tiger Kids KF94 with 99.4% FE

Bluna Kids KF94 with 98.8% FE

BOTN Kids KF94 with 99.3% FE

HappyLife Goodsay Youth KF94 with 99.3% FE

Now that we have established what kinds of masks are necessary to keep us well-protected, we should expect the government to increase production of these masks, make them widely available and free for all! #maskup #maskswork ##maskmandates #covid19 #doctorsofinstagram #physiciansofinstagram