You should wear a mask at EAGs

By Alex W Zhu @ 2025-10-09T13:41 (+25)

I'm a Senior Analyst at the Johns Hopkins Center for Health Security and focus on pandemic prevention policy & research. One of my main areas of focus is improving indoor air quality to prevent spread of infectious diseases. 

A reprise of this post: 

EAG NYC is this weekend, we're approaching flu season, and we're ending a small summer wave of COVID.  

I plan to wear a KN95 mask at this EAG during large indoor group events, and plan to remove it during 1:1s, and I recommend you do the same. Edit: Even better, get a reusable respirator! 

Don't want to wear a mask? You can still avoid crowded indoor spaces and take your 1:1s outdoors. 

The Risks

90% of respiratory disease transmission occurs indoors. The most risky situation for transmission of respiratory infectious diseases is in large, crowded indoor spaces where nobody is masked. That's most of the conference, but especially talks & workshops. By this estimate, these settings are 29x riskier for catching COVID than your weekly normal risk.^[1] 

The Benefits

• You have a lower chance of getting sick!
  • Let's say wearing a mask reduces my chances of getting sick by 66%.^[2] If I value my work week at a simple $1000 for the money I make, not even accounting for the impact of that work, multiplied by my odds of getting sick (for me, this has been 4 of the past 8 EAGs, 50%. For you this is probably lower, let's say 5%), we'd get an EV of $667 saved for wearing a mask for me, and $67 for you if you think you have a 5% chance of getting sick.^[3] This EV is not including the costs associated with suffering, caretaking, Long COVID, other post-viral sequelae, potential costs of getting someone else sick & continuing a chain of illness, etc.
• You have a lower chance of getting other people sick.
  • You could be an asymptomatic transmitter of COVID, flu, or other respiratory diseases and you may never know. This is one of the reasons COVID was able reach the level of a pandemic.  Wearing a mask reduces the chances of asymptomatic spread.
  • You make it safer for other people. The more people who wear masks, the safer everyone is from respiratory diseases. You protect people who are immunocompromised. You might think your immune system is fine, but others' may not be, and it may not be easy to tell. Or maybe they're taking care of older people who are more susceptible to COVID and flu. Or maybe they have long COVID or don't want to get long COVID. Or many other reasons.

The Costs

• Lost social benefits from facial expressions / recognition
  • I acknowledge that this can be costly depending on your value of these cues, so if you're comfortable, I think it's fair to take off your mask for 1:1s, and have meetings outside or away from large crowds
• Inconvenience
  • You have to think about it and act intentionally to put it on / take it off. Let's say maybe this costs $10 of your mental energy? Still worth it.  
• Cost of a mask: $1 (the conference in the past has provided these for free)

What else can we do?

• Generally avoid crowded indoor spaces, go outside if possible for 1:1s.  
• Could EAG implement personal air cleaners throughout the big rooms for better ventilation / filtration? Or implement FAR-UV?
• Take Zinc Lozenges prophylactically? If I were to, I'd do twice a day during the conference in the morning and after lunch.
• Nasal sprays were suggested in the comments of my previous post, though the evidence is sparse, in my opinion, and this is worse than masking in terms of actively having to apply it & think about it. 

I encourage you to wear a mask when you can at EAGs. One of our cause areas is pandemic prevention. This is part of that as well. Thank you :)

Thanks to Finan Adamson & Biak Tial for a quick review. Thanks Finan for sharing Microcovid

1. ^{^}

   https://www.microcovid.org/?casesPastWeek=150&distance=close&duration=60&interaction=oneTime&personCount=25&riskProfile=average&scenarioName=smallIndoorParty25&setting=indoor&theirMask=none&voice=normal&yourMask=none&yourVaccineDoses=3&yourVaccineType=moderna

2. ^{^}

   You can play with the settings here: https://www.microcovid.org/?casesPastWeek=150&distance=normal&duration=60&interaction=oneTime&personCount=25&riskProfile=average&scenarioName=smallIndoorParty25&setting=indoor&theirMask=none&voice=normal&yourMask=none&yourVaccineDoses=3&yourVaccineType=moderna

3. ^{^}

   50% Risk Scenario

   Without a mask:

   • 50% chance of getting sick and losing $1,000
   • 50% chance of staying healthy and keeping $1,000
   • Expected value = (0.50 × -$1,000) + (0.50 × $1,000) = -$500 + $500 = $0

   With a mask (reduces risk by 66.6%, so risk becomes 16.7%):

   • 16.7% chance of getting sick and losing $1,000
   • 83.3% chance of staying healthy and keeping $1,000
   • Expected value = (0.167 × -$1,000) + (0.833 × $1,000) = -$167 + $833 = $666

   Expected value of wearing the mask = $666 - $0 = $666

   5% Risk Scenario

   Without a mask:

   • 5% chance of getting sick and losing $1,000
   • 95% chance of staying healthy and keeping $1,000
   • Expected value = (0.05 × -$1,000) + (0.95 × $1,000) = -$50 + $950 = $900

   With a mask (reduces risk by 66.6%, so risk becomes 1.67%):

   • 1.67% chance of getting sick and losing $1,000
   • 98.33% chance of staying healthy and keeping $1,000
   • Expected value = (0.0167 × -$1,000) + (0.9833 × $1,000) = -$16.70 + $983.30 = $966.60

   Expected value of wearing the mask = $966.60 - $900 = $66.60

   With the higher mask effectiveness of 66.6%, the expected value increases proportionally:

   • At 50% baseline risk: mask value = $666
   • At 5% baseline risk: mask value = $66.60

   The general formula becomes: Expected value of mask = Initial risk × $666

   Courtesy of AI