Thread by @CzypionkaThomas

1/ There has been a lot of incorrect information lately regarding the use of masks on public transportation. I'll try to put this in the proper perspective here. Upon multiple requests, here are may two latest threads in English about #masks and #masking on #publictransport

2/ Masks are an effective means of preventing infection. However, masks are not only used for self-protection, but also for the protection of others, because masks
1) have a multiplicative effect, i.e. the filter effect is strongly increased if the infected person and the

3/ healthy person both wear a mask
2) are not 100% effective, i.e. it is very important whether the aerosol load in a room is low (high number of mask wearers) or high (few mask wearers).

4/ It was claimed that “hardly anyone would get infected on public transport anyway because the contact period is short.”

1)The contact period is not short if someone commutes to a city centre

2)The higher the aerosol load, the shorter the required contact time,

5/ i.e. even within 5 minutes I can get infected if a subway car or tram is crammed 3)Transmission by ballistic droplets takes only one second at all, because the larger droplets easily already contain the minimum infectious dose. This is important in public transport, where the

6/ distance is very short.
4)The only reason why public transport does not appear in many cluster analyses is that many people can well remember on which days they were in their offices, but hardly anyone can remember the exact train on a subway line they

7/ took from. Thus, a cluster cannot be identified. It has sometimes been claimed that “if people do not catch the disease in public transport, they catch it somewhere else.” This assumption is IMHO based on an average-person-fallacy.

8/ 1)This false assumption easily arises while abstracting or modeling, because one has to reduce the multitude of possibilities. But not everyone goes to a restaurant 0.2 times per day and to a concert 0.05 times per day. There are numerous people, especially vulnerable ones,

9/ for whom public transport is the only significant source of infection.
2)Moreover, public transport is a place with very high risk of infection, and at the same time, it is one of the few places that vulnerable people can hardly avoid.

10/ Claim: “In case of Omicron, the mask is not effective anyway.”
1)Especially with Omicron, the FFP2 mask is very effective
2)This is because the infection does not reach that deep. The higher up in the airways, the larger the aerosols containing virions and thus the easier

11/ to filter.

3)The higher contagiousness of Omicron is due to the higher number of virions in these larger aerosols.

12/ Claim: "Covid numbers are still low at the moment. The hospitals are quiet anyway." 1)However, other ILIs such as RSV and increasingly influenza are circulating massively.
2)Masks are even more effective against these than against SARS-CoV-2.

13/ 3)There has been no quiet in the hospitals since the beginning of the pandemic, and the staff has the right to expect the population to show consideration!
4)Why should we wait for the next disaster (Covid+Influenza+ILIs) before we act?

14/ Claim: "Other countries have no mask obligation in public transport"
1)In some countries it does still exist, in many countries masks are strongly recommended and also worn
2)It should make us think that this trust in politics and authorities is missing It is most

15/ regrettable that many countries did not succeed in learning lessons from the pandemic and emerging stronger from it. We have seen how important infection prevention is. And it would have been better for all of us if we had learned that

16/ it makes sense to wear masks more often in winter in high-risk settings. Instead, policymakers have created resistance to beneficial measures, not least by attempting to impose general vaccination mandates, but also by not caring enough about health literacy.

17/ This will be a disadvantage to all of us and to our society at large.

18/ This previous thread on #masks in public transport has obviously caused quite a stir and I thank many of you for the great encouragement! It was important for me to communicate two main aspects:

19/ 1) I wanted to clarify incorrect statements and errors in thinking that have been voiced recently.
2) I think it is unfortunate that, as a society, we have not grown from facing the challenge of the pandemic, but rather have become divided.

20/ In the years before, we dismissed infectious diseases too lightly. We tolerated coughing people in crowded waiting rooms right next to heart patients. We accepted that our children and we ourselves are sick a few times every fall/winter.

21/ Particularly #LongCovid has drawn attention to the fact that infectious diseases can cause permanent defects, and moreover can also lead to #MECSF-like symptoms through diverse immunological and cellular mechanisms. In addition, infectious diseases lead to economic losses.

22/ We would not have to endure all this. We could be in a better position, now and in the future. However, besides the encouragement, there were also a few "counter-tweets" showing a lack of knowledge on the part of their originators, their lack of ability

23/ to interpret scientific results, and sometimes, unfortunately, their lack of self-assessment. (People who know perfectly well that viruses are, after all, far too small to be filtered by masks.)

24/ People who, without ever having calculated more than an average, are firmly convinced that they know best what studies can do and what should have been proven long ago. Individuals who believe that they have

25/ all the wisdom in the world by mentioning words like "null hypothesis" or "RCT". Individuals who are convinced that I am only writing this to help political parties, although I have been just as critical of uncontrolled testing, which they promoted.

26/ Why do I think I can give an educated opinion on the topic? I have published several papers on Covid-19 as well as on masks and infection control and have exchanged knowledge on these topics with hundreds of other scientists in expert groups.

27/ In addition, we have conducted numerous quantitative and qualitative projects on Covid-19 in my research group at @IHSvienna. Our project @PER1SCOPE_EU addresses how to better prepare our practices and hospitals for pandemics.

28/ The project @SUNRISE_Europe looks at how critical infrastructures can be better protected in the event of shocks such as pandemics. Precisely because we are successfully researching and generating evidence, I unfortunately do not have the time to comment on all tweets.

29/ Additionally, the wording often suggests that the goalpost has already been readied for being moved... Another difficulty is that many of these issues are very complex and citing one study is often not actually bona fide - perhaps five others exist that suggest the contrary.

30/ Only an overview of current scientific knowledge would give a more or less complete picture, and tweets can hardly accomplish that. However, I will gladly cite illustrative studies on some points. However, I am concerned that while

31/ 1) Tomorrow's world will be a knowledge-based one
2) We need knowledge to cope with global problems
3) Knowledge is one of European countries’ most essential resources in international competition
4) Science skepticism seems to be on the rise and

32/ 5) Some politicians, journalists and other stakeholders are also turning into multipliers of non-scientific statements.

This by no means applies only to medical topics, nor to one "side".

33/ Ideologues come in all flavors, and the interpretation of science is also shaped by one's own opinion.

34/ Finally, here are some more publications on the subject of masks and public transport, with DOI for brevity:
1) Transmission of Covid-19 in public transport
a. ...was impressively shown by employees of this industry e.g. here: 10.15585/mmwr.mm7133a4

35/ “Outbreak incidence was 5.2 times as high (129.1 outbreaks per 1,000 establishments) in the bus and urban transit industry and 3.6 times as high in the air transportation industry (87.7) as in all California industries combined (24.7)”

36/ b. For NY, reductions in commuting were shown to correlate directly with the spatial distribution of number of cases (10.1038/s41467-020-18271-5), similar to China (10.1126/science.abb4218)

37/ c. A recent Norwegian study shows a correlation of infections and use of public transport in Norway 10.1186/s12879-022-07233-5
d. Reviews of cluster analyses from other countries also show public transport as a source of infection, e.g., 10.1016/j.ijid.2020.07.073 2)

38/ Effectiveness of masks: In addition to our own narrative reviews from 2020 (10.1136/bmj.m1435) and 2021 (10.7326/M20-6625) @trishgreenhalgh , here are other large reviews (published after that), all showing the protective effect of masks against SARS-CoV-2:

39/ a. 10.1002/rmv.2336 („Our study confirmed that the use of facemasks provides protection against respiratory viral infections in general; however, the effectiveness may vary according to the type of facemask used.),

40/ b. 10.1183/23120541.00650-2021 („Evidence for the use of hand hygiene or facemasks is the strongest“) ,
c. 10.1038/s41398-022-01814-3 (“The meta-analysis of RCTs found a significant protective effect of facemask intervention (OR = 0.84; 95% CI = 0.71-0.99; I2 = 0%)”)

41/ 3) Effectiveness of masks on public transport:
a. Study from Germany, that estimates effectiveness based on regional distribution of mandatory masks in public transport:

42/ 10.1073/pnas.2015954117 (“[…]we find that face masks reduced the number of newly registered severe acute respiratory syndrome coronavirus 2 infections between 15% and 75% over a period of 20 days after their mandatory introduction”)

43/ b. Study from South Korea: 10.1126/sciadv.abg3691 („Mandatory wearing of masks and practicing social distancing with masks during peak hours reduced infection rates by 93.5 and 98.1%, respectively.”

44/ c. Study from Vietnam/Hanoi, where mask compliance is close to 100%. 10.1016/j.jth.2021.101279 (“Hanoi's overall measures - full use of face masks and partial use of hand sanitizer - were sufficient to contain three relatively minor

45/ Covid-19 waves while still maintaining regular bus operations most of the time.”) d. Study from Australia/Sydney 10.1186/s12879-022-07664-0 , whose title says it all “SAfE transport: wearing face masks significantly reduces the spread of COVID-19 on

46/ trains” Finally, a publication that shows that randomized controlled trials are by no means always conclusive: "Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial" (10.1136/bmj.k5094) This RTC shows

47/ that parachutes have no effect on the probability of death or injury when jumping from an aircraft. „Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention. However,

48/ the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps. When beliefs regarding the effectiveness of an intervention exist in the community, randomized trials

49/ might selectively enroll individuals with a lower perceived likelihood of benefit, thus diminishing the applicability of the results to clinical practice.”