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# System prepended metadata

title: The case for strong COVID precautions at conferences

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# The case for strong COVID precautions at conferences

Conferences inherently create environments that facilitate the spread of infectious diseases, by bringing people together from various parts of the world — many of whom will have been in recent close proximity to large numbers of people due to air travel. Given the infectivity and immune-evasion capabilities of newer COVID-19 variants, it is almost a statistical certainty that there will be COVID-positive attendees at any typical conference.

Two-way masking with FFP2/N95 or better masks, that is, masking *by all participants and not just by those who know they are at greater risk*, is the most effective means of preventing COVID transmission and consequent risks to health.

## Recent variants are significantly more transmissible and able to evade immune protection from current vaccines

> **Enhanced transmissibility, infectivity, and immune resistance of the SARS-CoV-2 omicron XBB.1.5 variant**
>
> In late 2022, the SARS-CoV-2 omicron BQ.1 and XBB lineages, characterised by amino acid substitutions in the spike protein that increase viral fitness, had become predominant in the western (BQ.1) and eastern (XBB) hemispheres. The BQ.1 lineages are descendants of BA.5, whereas the XBB lineage is the recombinant of two highly diversified BA.2 lineages.
> [...]
> Experiments using lentivirus-based pseudoviruses also showed approximately 3-fold increased infectivity of XBB.1.5 compared with XBB.1. These results suggest that XBB.1.5 exhibits a remarkably strong affinity to the human ACE2 receptor, which is attributed to the S486P substitution. Moreover, neutralisation assay revealed that XBB.1.5 was robustly resistant to BA.2 breakthrough infection sera (41-fold versus B.1.1, 20-fold versus BA.2) and BA.5 breakthrough infection sera (32-fold versus B.1.1, 9.5-fold versus BA.5).
> [...]
> In summary, our results suggest that XBB.1.5 is the most successful XBB lineage as of January, 2023, as it has acquired the S:S486P substitution, which enhances its binding affinity to the ACE2 receptor without compromising its remarkable immune resistance. Our data suggest that these virological features result in greater transmissibility.
>  
―[The Lancet Infectious Diseases, January 31, 2023](https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(23)00051-8/fulltext)

> **Extraordinary Evasion of Neutralizing Antibody Response by Omicron XBB.1.5, CH.1.1 and CA.3.1 Variants**
>
> Newly emerging Omicron subvariants continue to emerge around the world, presenting potential challenges to current vaccination strategies. This study investigates the extent of neutralizing antibody escape by new subvariants XBB.1.5, CH.1.1, and CA.3.1, as well as their impacts on spike protein biology. Our results demonstrated a nearly complete escape of these variants from neutralizing antibodies stimulated by three doses of mRNA vaccine, but neutralization was rescued by a bivalent booster. However, CH.1.1 and CA.3.1 variants were highly resistant to both monovalent and bivalent mRNA vaccinations. We also assessed neutralization by sera from individuals infected during the BA.4/5 wave of infection and observed similar trends of immune escape.

―[Panke Qu, Julia N. Faraone, John P. Evans, Yi-Min Zheng, Claire Carlin, Mirela Anghelina, Patrick Stevens, Soledad Fernandez, Daniel Jones, Ashish Panchal, Linda J. Saif, Eugene M. Oltz, Kai Xu, Richard J. Gumina, Shan-Lu Liu. bioRxiv preprint (not peer-reviewed), January 17 2023](https://www.biorxiv.org/content/10.1101/2023.01.16.524244v1)

This is on top of previous increases in transmissibility and vaccine escape for Omicron strains relative to the Delta lineage. The XBB.1.5 strain, or another even more transmissible strain that evolves from it, is [likely to be dominant in Europe within a few months](https://www.ecdc.europa.eu/sites/default/files/documents/TAB-Implications%20for%20the%20EU-EEA%20of%20the%20spread%20of%20the%20SARS-CoV-2%20Omicron%20XBB.1.5%20sub-lineage.pdf).

## COVID is airborne

Early in the pandemic (before mid-2020), there was insufficient evidence to say whether or not COVID was spread mainly by large droplets (most of which would fall to the ground relatively quickly), or by microdroplets that can persist for long periods as aerosols. The latter is called "airborne transmission". However, it was definitively resolved quite early on that COVID-19 does spread primarily through airborne transmission (see for example [this article](https://covid19.nj.gov/faqs/coronavirus-information/about-the-virus/is-the-coronavirus-airborne) from New Jersey COVID-19 Information Hub in September 2020).

There was *considerable* political resistance to making this point clear to the wider public or even to front-line health workers, but it was not scientifically in doubt among competent epidemiologists after, at the latest, the end of 2020.

COVID-carrying microdroplets can remain in the air for several hours:

> When people with the COVID-19 infection breathe out, clear their throats, cough, sneeze, speak, or otherwise move air out through their nose or mouth, droplets of all different sizes, which can contain the virus, are ejected into the air. A substantial portion of people infected with SARS-CoV-2 - around 40 percent - wouldn't even know they are ejecting virus-laden droplets, as they may not exhibit symptoms.
> Droplets suspended in the air are called an aerosol. Droplets that are large can remain in the air for seconds to minutes before falling to the ground. Smaller droplets stay in the air longer – minutes to even hours.

―[New Jersey COVID-19 Information Hub, September 2020](https://covid19.nj.gov/faqs/coronavirus-information/about-the-virus/is-the-coronavirus-airborne)

## Transmission is often from asymptomatic people

Transmission from infected people with no symptoms is very common, possibly accounting for the majority of all SARS-CoV-2 transmission.

> **Findings**  In this decision analytical model assessing multiple scenarios for the infectious period and the proportion of transmission from individuals who never have COVID-19 symptoms, transmission from asymptomatic individuals was estimated to account for more than half of all transmission.
> **Meaning**  The findings of this study suggest that the identification and isolation of persons with symptomatic COVID-19 alone will not control the ongoing spread of SARS-CoV-2.

―[SARS-CoV-2 Transmission From People Without COVID-19 Symptoms, January 2021](https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774707)

It’s not possible to be sure one is free of COVID, even with testing. This means that it is not sufficient for attendees to rely only on isolating if they get symptoms or if they have a positive test.

## The popular narrative that COVID is getting "milder" is oversimplified

> A now-famous report from Imperial College London published on December 22 found that COVID-19 patients infected with Omicron had a 20 to 25 percent reduced risk of hospitalization compared to those with Delta, and a 40 to 45 percent reduced risk of a hospital stay that lasted one or more days—which the researchers used as an indicator of severe cases.
> That discovery helped fuel a narrative, popular in the media, that Omicron is mild. But Omicron was first detected in South Africa, a country with a relatively young population of people who are largely either vaccinated, already recovered from COVID-19, or both. That made it hard, experts tell The Scientist, to tell whether Omicron’s severity was really a step back from Delta’s, or if, instead, any new variant emerging this late into the pandemic would seem less severe due to the acquired immunity and clinical knowledge that’s built up over time.

―[How Mild Is Omicron Really?. The Scientist. Dan Robitzski, January 2022](https://www.the-scientist.com/news-opinion/how-mild-is-omicron-really-69610)

> The researchers [from the LKS Faculty of Medicine at The University of Hong Kong] found that Omicron SARS-CoV-2 infects and multiplies 70 times faster than the Delta variant and original SARS-CoV-2 in human bronchus, which may explain why Omicron may transmit faster between humans than previous variants.

―[HKUMed finds Omicron SARS-CoV-2 can infect faster and better than Delta in human bronchus but with less severe infection in lung. University of Hong Kong, December 2021](https://www.med.hku.hk/en/news/press/20211215-omicron-sars-cov-2-infection)

> The newer subvariants [BA.4 and BA.5] can also bypass monoclonal antibody treatments, which use lab-made immune system proteins developed from earlier strains of SARS-CoV-2. “Most of those antibodies that have been made are now obsolete,” Bieniasz says. Only one such treatment made by Eli Lilly, specifically designed to work against Omicron, is now effective and in use.

―[What to Know About the Newest, Most Contagious Omicron Subvariants. TIME, June 2022](https://time.com/6187762/ba-4-ba-5-omicron-subvariants-symptoms-risk/)

> A note on Covid: July 6, 2021, when vaccines were less prevalent, the US was averaging about 14,000 new infection per day. One year later, we’re at 114,000. One year ago, we were averaging 260 covid deaths per day; now we are closing in on 400 per day [in the US]!

―[Dan Goldberg, July 2022](https://twitter.com/DanCGoldberg/status/1544506315678130177)

> I can warn you based on our patients. 
> BA.5 may be the most dangerous strain yet or the reinfections are becoming more severe. But young people are getting pretty f*cked up from it.

—[Alex Meshkin, G.E.D., July 2022](https://mobile.twitter.com/alexmeshkin/status/1544891165102600194)

## The risk of Long COVID and other adverse outcomes increases with each reinfection

> Finally, there is the “dose-response” effect of multiple reinfections. By that I mean with additional episodes of Covid, for every outcome there was a stepwise increased risk, both relative (left panel) and absolute (right panel).
>
> ![Figure showing increasing risk of various adverse outcomes after 1, 2, and 3 infections](https://i.imgur.com/lV31PaK.png =500x)
>
> Obviously these findings are worrisome since reinfection was quite rare before the Omicron wave hit, at 1% or less through the Delta variant wave. But now reinfections have become much more common. Why? The Omicron BA.2, BA.2.12.1, BA.4, and BA.5 have progressively increased immune escape and there is limited cross-immunity with BA.1, the Omicron version that about half of Americans got infected with early in 2022.

―[A reinfection red flag — Why a new report is so troubling. Eric Topol, June 2022](https://erictopol.substack.com/p/a-reinfection-red-flag)

> Compared to no reinfection, reinfection contributed additional risks of death (hazard ratio (HR) = 2.17, 95% confidence intervals (CI) 1.93–2.45), hospitalization (HR = 3.32, 95% CI 3.13–3.51) and sequelae including pulmonary, cardiovascular, hematological, diabetes, gastrointestinal, kidney, mental health, musculoskeletal and neurological disorders. The risks were evident regardless of vaccination status. The risks were most pronounced in the acute phase but persisted in the postacute phase at 6 months. Compared to noninfected controls, cumulative risks and burdens of repeat infection increased according to the number of infections.
>
> ![](https://i.imgur.com/Jd63CcL.png)

―[Acute and post-acute sequelae associated with SARS-CoV-2 reinfection. Benjamin Bowe; Yan Xie; Ziyad Al-Aly. Nature Medicine volume 28, 2022](https://www.nature.com/articles/s41591-022-02051-3)

## Clinically vulnerable attendees and their families are not a corner case

Some people are especially vulnerable to the effects of COVID. This includes not only attendees, but their families after they return home. Attendees should not be put in the position of having to accept a higher risk of serious adverse outcomes for them and their families that could have been avoided if stronger protections were in place.

Clinical vulnerability cannot be treated as an afterthought when deciding on conference COVID policies.

> All people with serious underlying chronic medical conditions like chronic lung disease, a serious heart condition, or a weakened immune system seem to be more likely to get severely ill from COVID-19. Adults with disabilities are three times more likely than adults without disabilities to have heart disease, diabetes, cancer, or a stroke.

―[CDC COVID-19 Information and Resources — People with Disabilities](https://www.cdc.gov/ncbddd/humandevelopment/covid-19/people-with-disabilities.html)

―[CDC COVID-19 Information and Resources — People with Certain Medical Conditions](https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-with-medical-conditions.html)

These health risks combine with pre-existing discrimination and exclusion of disabled people, which is a particular issue for participation in scientific conferences.

> "While many persons with disabilities have health conditions that make them more susceptible to COVID-19, pre-existing discrimination and inequality means that persons with disabilities are one of the most excluded groups in terms of health prevention and response actions and economic and social support measures, and among the hardest hit in terms of transmission risk and actual fatalities."

―[UN Committee on the Rights of Persons with Disabilities, June 2020](https://www.ohchr.org/en/news/2020/06/statement-covid-19-and-human-rights-persons-disabilities)

## Government recommendations are not enough

> It doesn't require a doctorate to understand the Biden administration is downplaying the short and long-term risks of COVID due to economic and political considerations. In fact, having a doctorate and certain career ambitions might be an impediment to understand that.
> I have sat in meetings where people who work for state and local health departments have explained that they wanted to implement mask mandates but were overruled by mayors or governors in overwhelmingly liberal jurisdictions.

―[Justin Feldman (Health and Human Rights Fellow at Harvard), July 2022](https://twitter.com/jfeldman_epi/status/1543676706485161984)

> **Covid response ‘one of UK’s worst ever public health failures’**
>
> Britain’s early handling of the coronavirus pandemic was one of the worst public health failures in UK history, with ministers and scientists taking a “fatalistic” approach that exacerbated the death toll, a landmark inquiry has found.
>
> “Groupthink”, evidence of British exceptionalism and a deliberately “slow and gradualist” approach meant the UK fared “significantly worse” than other countries, according to the 151-page “[Coronavirus: lessons learned to date](https://committees.parliament.uk/publications/7496/documents/78687/default/)” report led by two former Conservative ministers. The crisis exposed “major deficiencies in the machinery of government”, with public bodies unable to share vital information and scientific advice impaired by a lack of transparency, input from international experts and meaningful challenge.

―[The Guardian, October 2021](https://www.theguardian.com/politics/2021/oct/12/covid-response-one-of-uks-worst-ever-public-health-failures)

> As a sort-of newcomer [to the Netherlands], I’ve also realized that some of the things I originally admired about this country have turned out to be critical weaknesses. When I arrived in the Netherlands years ago, after working as a political adviser in London, I remember being amazed by how grown-up Dutch politics seemed, with its constant emphasis on evidence and compromise. If Westminster felt like a boxing ring where everyone was constantly furious with one another, the Hague was more like a friendly club or university, filled with kind, clever people who worked together to get things done. Things moved slowly, but when living below sea level, it paid to not make any sudden moves.
>
> In normal times, this difference-splitting often worked fantastically well, helping the Netherlands become one of the wealthiest, safest and happiest societies in the world. Yet it’s become clear that during a crisis, these same mechanisms can lead to paralysis.
>
> One example of this was the infamous debate over masks. The WHO recommended that masks should be worn in confined public spaces on 5th June [2020]. The UK made masks mandatory on public transport on 15th June, and in shops from 24th July. France made masks mandatory in shops in late July, and even McDonald’s in the US made them mandatory for customers from 1st August. In the sensible Netherlands, however, the simple act of wearing a mask somehow remained as controversial as Zwarte Piet.
>
> Faced with a situation where there was an urgent need to do unpopular things, the authorities wasted months dithering and debating. Mayors told people to wear masks, the RIVM told them not to bother, and ministers seemed unable to decide either way. As a result of all this, masks didn’t become compulsory in public until 1st December [2020] – four months after McDonalds – by which point nearly ten thousand Dutch people had died, including (presumably) some who might have lived if mask-wearing had been routine.

―[Dutch exceptionalism: Superior failure in the year of coronavirus. Ben Coates, February 2021](https://www.dutchnews.nl/features/2021/02/dutch-exceptionalism-superior-failure-in-the-year-of-coronavirus/)

## It has been common for conferences to require some combination of masks, vaccination, and testing

### RustConf 2022

> * Masks are required indoors and when unable to socially distance outdoors
> * Full vaccination is required for all event participants and on-site vendors; you will receive an email several weeks before the conference with instructions on how to securely provide your documentation for advance verification.
> * Testing will be required as well, at-home or PCR; depending on what the pandemic looks like closer to August. We are operating on the side of being as cautious as possible so that our attendees will be as safe and comfortable as possible.
> 
> **Is testing accepted in lieu of vaccines?**
>
> No. Testing is required in addition to proof of fully vaccinated status. SafeAccess will accept either LFT/OTC tests, or PCR tests, from ~24h pre-conference, as proof of vaccination. In the US, all at-home/OTC LFT tests currently authorized by the US FDA are acceptable.

―[RustConf 2022 FAQ — COVID-19 policies](https://rustconf.com/about#covid-precautions)

### DEF CON 29 (2021)

> **Masks and Vaccination will be required at DEF CON 29 this year, thanks to the complications of COVID-19.**
>
> While the virtual portion will largely be the same as DEF CON Safe Mode, in-person DEF CON 29 will be guided by safety and number of attendees.
>
> Vaccination and wearing a mask while in the DEF CON space will be required. No exceptions. Persons who are not vaccinated, including unvaccinated children, will not be admitted. 

―[DEF CON 29 FAQ](https://defcon.org/html/defcon-29/dc-29-faq.html)

### DEF CON 30 (2022)

> [...] There are still new variants on the move. There are still spikes in transmission and hospitalization. Masks are still the most effective way to protect people in indoor events.
> Barring a major change in the situation, we will not check proof of vaccination, but we will keep last year's mask requirement in place for DEF CON 30. Protecting the community is our first priority, and we want to make sure that everyone is as safe as we can make them. Everyone includes the healthy, the vulnerable and those who have immune compromised loved ones they need to protect.

―[COVID Updates for DEF CON 30, May 2022](https://defcon.org/html/links/dc-news.html#dc30covid)

### EGOS 2022

> #egos2022 conference kit includes Lego pieces, face mask, rapid tests and instructions to test, wear, and being safe

―[Tina Dacin, July 2022](https://twitter.com/TinaDacin/status/1544232309628583939)

### HACS 2022

> The HACS workshop was held in Amsterdam April 2022 over two days, indoors, with over 100 attendees from around the world. Masks (surgical or better) were required when not eating or drinking,  and provided (N95s and others). Rapid antigen tests were provided, administered and verified each morning by organizers in a dedicated space before entering the workshop areas. Vaccination was verified before arrival to the conference. The workshop spaces were well spaced and decently ventilated, although we could not obtain specific metrics on HVAC ventilation grades or number of air changes over time.  HACS reported one attendee that tested positive 2 days after the workshop.

### Zcon3 (2022)

> In response to community feedback, and in consideration of continued high levels of incidence, we are updating the COVID precautions and guidance for Zcon3 as follows: 
>
> * **Masks will be required for all attendees.** [In the event, N95+ masks were provided, partly due to the efforts of clinically vulnerable attendees, although the FAQ was not updated to reflect this. ―Daira]
> * Vaccinations and boosters are not required. However, they are encouraged for all attendees, in accordance with the health guidance provided by your country of residence. 
> * Negative tests are not required. While we will not require a negative test for admission, we will provide one rapid antigen nasal test in each attendee swag bag that we hand out at registration. If you anticipate the need to test more than once during Zcon3, we urge you to bring your own tests to ensure a sufficient supply. Similarly, if your preference is saliva tests, we urge you to bring your own tests.

―[Zcash Foundation. Zcon3 FAQ, 2022](https://zfnd.org/zcon3-3/)

## Evidence in favour of N95+ over cloth or surgical masks

Definition: an N95+ mask is a mask that filters out at least 94% of particles 0.3 microns (0.3 μm) or above. This includes FFP2 masks (the European equivalent of N95) and N99 or FFP3 masks (which provide at least 98% filtration of partices 0.3 microns or above).

―[What Are the Differences between FFP3, N95, And Surgical Masks? October 2021](https://www.protectivemasksdirect.co.uk/blog/what-are-the-differences-between-ffp3-n95-and-surgical-masks/).

### Why N95+ masks provide adequate protection, and cloth masks much less so

The critical point in reducing transmission of an airborne viral disease through mask wearing, is to make sure that microdroplets containing virus particles are caught by the mask. This can be either the mask of the infected person as they breathe out, or the mask of the potential infectee as they breathe in. (The reason why N95+ masks are multi-layer is to attempt to stop any caught virus particles from migrating through the mask, at least until those particles are no longer infectious.)

It typically takes [between a few hundred and a few thousand](https://www.webmd.com/lung/news/20201105/dose-of-coronavirus-timing-matters-for-infection) inhaled virus particles to catch COVID. Estimates of how long airborne virus particles retain their ability to transmit COVID vary from [around 20 minutes](https://www.healthline.com/health-news/how-long-is-the-coronavirus-infectious-when-its-in-the-air) to [three hours](https://covid19.nj.gov/faqs/coronavirus-information/about-the-virus/is-the-coronavirus-airborne). Virus particles caught by a mask stay infectious for about the same time unless the mask is impregnated with antivirals (which most masks are not). The time for which microdroplets remain in the air also varies from minutes to hours, depending on their size and on air movement.

Because cloth masks normally have a single, somewhat permeable layer, they are much less effective at keeping virus particles that are caught when inhaling from infecting the wearer. They are also less effective at catching particles that are breathed out by an infected person. This is because they are usually less closely fitted, and because many particles are small enough to just go through the mask.

> It is known that respiratory protective equipment is only effective when there is an adequate seal formed between a mask and the person’s face to ensure that inhaled air is actually filtered. Indeed, research has suggested that an ineffective seal is the primary cause of airborne contamination amongst wearers of face masks [[3]](https://www.tandfonline.com/doi/abs/10.1080/15298668391405634). It has been noted that leakage around the face mask may account for a third of airflow across surgical masks and a sixth of the flow across respirators [[3]](https://www.tandfonline.com/doi/abs/10.1080/15298668391405634). Fit is recognized as being particularly important when determining whether masks are capable of reducing the spread of fine particles.

―[Comparing the fit of N95, KN95, surgical, and cloth face masks and assessing the accuracy of fit checking. PLOS ONE, January 2021](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245688#pone.0245688.ref003)

The benefits of fit checking should not be interpreted as implying that N95+ masks are not effective without a professional fit test, however. Ensuring that [the nose bridge of an N95+ mask is properly pressed down, and that straps are not loose](https://twitter.com/Thatquaratined1/status/1472784182216593411) goes a long way to reducing leakage.

The following studies compare the effectiveness of N95+ vs cloth masks:

* [A comparison of performance metrics for cloth masks as source control devices for simulated cough and exhalation aerosols. Aerosol Science and Technology, May 2021](https://www.tandfonline.com/doi/full/10.1080/02786826.2021.1933377)
  > Collection efficiencies [of ≤7 micron particles] for the cloth masks ranged from 17% to 71% for coughing and 35% to 66% for exhalation. Filtration efficiencies for the cloth masks ranged from 1.4% to 98%, while the fit factors were 1.3 to 7.4 on headforms and 1.0 to 4.0 on human subjects.
  >
  That is, the filtration effectiveness of cloth masks varies over a wide range, and cannot be relied on. (The "cloth mask" that reached 98% filtration efficiency in this study was not a typical example of a cloth mask, it just wasn't certified as an N95.)
* [Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021](https://www.cdc.gov/mmwr/volumes/71/wr/mm7106e1.htm)
  > Wearing an N95/KN95 respirator (aOR = 0.17; 95% CI = 0.05–0.64) or wearing a surgical mask (aOR = 0.34; 95% CI = 0.13–0.90) was associated with lower adjusted odds of a positive test result compared with not wearing a mask (Table 3). Wearing a cloth mask (aOR = 0.44; 95% CI = 0.17–1.17) was associated with lower adjusted odds of a positive test compared with never wearing a face covering but was not statistically significant.
  ![](https://i.imgur.com/aXpLpz7.png)

### Distributing N95+ masks to all attendees is affordable

Individually sealed N95+ masks are available at a cost per mask of about 1 USD or 1 EUR. FFP3 masks are about 2 USD or 2 EUR each. Providing sufficient masks for all attendees is well within the means of most conferences.

### What about surgical masks?

N95+ masks are just as comfortable to wear as surgical masks (in my experience, more so for at least some brands), and the evidence shows they are much more effective. In particular, surgical masks inherently have poor fit due to their shape, compared to N95+ masks.

> Interestingly, [even] very loosely fitted FFP2 masks (case ff) outperform adjusted surgical masks (case SS) by a factor of 2.5. 

―[An upper bound on one-to-one exposure to infectious human respiratory particles. Gholamhossein Bagheri; Birte Thiede; Bardia Hejazi; Eberhard Bodenschatz. Proceedings of the National Academy of Sciences, December 2021](https://www.pnas.org/doi/10.1073/pnas.2110117118)

I have lost count of the number of times I've seen health professionals with surgical masks dangling loosely or having fallen below their nose.

## Policy Recommendations

### Masks

Masks are very effective at reducing the risk of transmission, especially non-valved N95/FFP2 or N99/FFP3 masks. They are most effective when *both* an infected person and a potential infectee are wearing them.

> Prior to the coronavirus disease 2019 (COVID-19) pandemic, the efficacy of community mask wearing to reduce the spread of respiratory infections was controversial because there were no solid relevant data to support their use. During the pandemic, the scientific evidence has increased. Compelling data now demonstrate that community mask wearing is an effective nonpharmacologic intervention to reduce the spread of this infection, especially as source control to prevent spread from infected persons, but also as protection to reduce wearers’ exposure to infection.

―[Effectiveness of Mask Wearing to Control Community Spread of SARS-CoV-2. John T. Brooks, MD; Jay C. Butler, MD. JAMA, February 2021](https://jamanetwork.com/journals/jama/fullarticle/2776536)

That is, although a vulnerable person can protect themself to some extent by wearing a mask, they are still at significant risk when breathing air near to an unmasked person who has COVID. We cannot know in advance who is infected; and so only universal mask wearing by all attendees of the conference can reliably reduce the risks for everyone.

> Our results show that face masks significantly reduce the risk of SARS-CoV-2 infection compared to social distancing. We find a very low risk of infection when everyone wears a face mask, even if it doesn’t fit perfectly on the face.
> [...]
> To calculate exposure and infection risk, we use a comprehensive database on respiratory particle size distribution; exhalation flow physics; leakage from face masks of various types and fits measured on human subjects; consideration of ambient particle shrinkage due to evaporation; and rehydration, inhalability, and deposition in the susceptible airways. We find, for a typical SARS-CoV-2 viral load and infectious dose, that social distancing alone, even at 3.0 m between two speaking individuals, leads to an upper bound of 90% for risk of infection after a few minutes. If only the susceptible wears a face mask with infectious speaking at a distance of 1.5 m, the upper bound drops very significantly; that is, with a surgical mask, the upper bound reaches 90% after 30 min, and, with an FFP2 mask, it remains at about 20% even after 1 h. When both wear a surgical mask, while the infectious is speaking, the very conservative upper bound remains below 30% after 1 h, but, **when both wear a well-fitting FFP2 mask, it is 0.4%** [emphasis added].

―[An upper bound on one-to-one exposure to infectious human respiratory particles. Gholamhossein Bagheri; Birte Thiede; Bardia Hejazi; Eberhard Bodenschatz. Proceedings of the National Academy of Sciences, December 2021](https://www.pnas.org/doi/10.1073/pnas.2110117118)

### Ventilation

Good ventilation is an important aspect of COVID mitigation. Venues should be chosen with this in mind, and it may be appropriate to add HEPA air filtration if the existing ventilation is not sufficient.

#### Ventilation During Meals and Drinks

Meals are high-risk super-spreader events, because people remove masks, sit across from each other, and talk. To lower the risk, meals and drinks should be held in a well-ventilated space, with well-spaced seating. The option for attendees to eat separately should always be provided. Conferences should be structured so that, as far as possible, attendees do not miss important content by taking this option.

## Testing

Attendees should be strongly encouraged to test for COVID *before* coming to registration, and in fact before travelling. It is a good idea to provide lateral flow tests in any case for those who may not have tested in advance. Anyone who experiences COVID symptoms or has a positive test should stay in their rooms, or outside if there is a safe place to go away from others. People experiencing symptoms should take another LFT even if they have already tested negative.

## Acknowledgements

This document was written mainly by Daira Emma Hopwood and Teor, with contributions from Kris Nuttycombe and Francisco Gindre.

# Closing remarks

The pandemic is not over. COVID-19 has caused 6.85 million deaths directly as of 10th February, 2023. This is an average of around 9,600 deaths per day since March 2020, with the current global death rate still being around 2,000 per day.

―[Coronavirus (COVID-19) Deaths. Our World in Data, accessed 12 February 2023](https://ourworldindata.org/covid-deaths#explore-the-global-data-on-confirmed-covid-19-deaths)

The World Health Organisation estimates that up to the end of 2021, the pandemic had caused 14.9 million excess deaths overall worldwide.

![](https://i.imgur.com/FkVeTkJ.png)

―[Estimates of Excess Mortality Associated with COVID-19 Pandemic. World Health Organisation, March 2022](https://www.who.int/data/sets/global-excess-deaths-associated-with-covid-19-modelled-estimates)

In the UK alone, 3% of the population (that is, 2 million people) are estimated to have Long COVID, of which 77% reported that it adversely affected their day-to-day activities.

―[Prevalence of ongoing symptoms following coronavirus (COVID-19) infection in the UK. Office for National Statistics (UK), February 2023](https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/prevalenceofongoingsymptomsfollowingcoronaviruscovid19infectionintheuk/2february2023)

It is important for decision-making processes about COVID precautions to take into account clinically vulnerable people when assessing risk. We know a lot more about how COVID is transmitted and its long-term risks than we did at the start of the pandemic. Unfortunately, the impression promoted to the general public by politicians and public health authorities has falsely minimized those risks.

The impression that COVID has become "mild" is not accurate. The evidence shows that one-way masking by people at greater vulnerability is not sufficient. Indeed, everyone is vulnerable to COVID, since the risk of long-term symptoms from a so-called "mild" case is in the region of 10%.

While no individual mitigation can eliminate risk, straightforward and noninvasive interventions like required masking and rapid testing as conditions for attendance help protect each of us both from the short-term discomfort (or worse) associated with an active infection, and the substantial long-term risks presented by COVID. Nobody wants to get sick at a conference, and nobody wants to suffer long-term cognitive (or other) harm.

I would like to quote [the strong words of Dr. David Berger](https://www.wsws.org/en/articles/2022/04/09/berg-a09.html), a General Practitioner who has been an outspoken critic of failed public health policies and debunker of myths about COVID:
> We are now infecting ourselves, and more critically, our children, repeatedly, with this virus that is rapidly mutating and changing its form, with no firm knowledge of the long-term consequences —which we can't have because we haven't had it for the long term— and if you looked simply in a risk management framework, that's insane. The risk that we're exposing ourselves to, is insane. And when we're doing it to the children we'd better watch out, because it's the children of today who write the history books of tomorrow, and they might be pretty pissed off with us. [...]
> And in talking about this I think particularly of anybody with a clinical vulnerability, anybody with diabetes, who is immunosuppressed on monoclonal antibodies or treatment for rheumatoid arthritis, or who's on steroids, or who has any other intercurrent morbidity, any other underlying illness. What we're effectively saying is "Well, you know, we've done our bit. We've protected you for two years, but it's just too much hassle now. We'll get on with it. The young and the fit, the vaccinated young and fit will probably be okay. Losses in that group, injury in that group will be acceptable. Rest of you, you know, do what you like and survive as you can."
> That's a pretty harsh position that we've adopted, really without a thought, and that everyone's taken on. It's old-style early 20th century eugenics. It's ableism. It says, those other people —the more frail people, the more vulnerable people, the people who do not fit to a certain ideal of physical perfection— tough luck.
>
> ―Dr. David Berger, April 2022

This finally gets some way toward a doctor expressing solidarity with the anger in the disability rights community about the public health failures that have left us out in the cold. It's not hyperbole at all, as [statistics about deaths](https://lordslibrary.parliament.uk/covid-19-pandemic-impact-on-people-with-disabilities/) and Long COVID among disabled and clinically vulnerable people show. By addressing the practical issues raised, conferences that adopt strong COVID precautions will be on the right side of history.

I believe that communities that pride themselves on respect for scientific rigour should apply the same rigour to public health policy as they do for their specialist fields. If you are a conference organiser, I hope that you will take into account the evidence provided above when deciding on COVID policy. If you are a potential attendee, I hope that this evidence helps you to make the case to organisers. Good luck!

―Daira Emma Hopwood, 2022 (updated February 2023)

