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As we approach the date announced by the Prime Minister to “unmask” the country (outdoors), confusion and controversy grows. It is not an exclusively Spanish phenomenon, and even in the scientific and health world there are opposing opinions.
Some are favorable to keeping the masks outdoors. In addition to a potential fear of future escape variants or the possible “disappearance” of immunity achieved with vaccination, the essential arguments seem to be:
psychological or sociological aspects, such as not giving the “signal” that the pandemic is over;
not have achieved group immunity and
the foreseeable increase in transmission in the (youngest) unvaccinated groups, associated with the enormous increase in contacts after the fall of the main restrictive measures and other factors (end of exams, summer mobility, local festivals, opening of hotels and leisure night, loss of fear of infecting our elders, etc.).
Other opinions are in favor of the removal of the masks. They are based on the low risk of outdoor transmission and the high proportion of vaccination among people at high risk of severe disease (the elderly).
In many ways, it is a minor controversy, like much of the controversy we’ve had during the pandemic. Let’s advance that outdoor masks, as long as the safety distance can be maintained, are clearly unnecessary. They are right now and surely they always have been.
Many countries have never applied this restriction outdoors. And in those who have, the objective seemed more “psychological” (accustoming to use), or a “demonstration” of political leadership (doing something, not being the last to do something), than epidemiological.
Let’s advance that indoors (and when you can’t keep your distance), masks are an essential measure. Essential. Although paradoxically we take them off at that time. And although indoors they are an insufficient measure and must be accompanied by cross ventilation, capacity limitation and other interventions.
Outdoor transmission is negligible
The available evidence on the low transmission capacity of SARS-CoV-2 in the open air is very strong. The rapid dissipation of aerosols (their main route of transmission) outdoors significantly hinders contagion. For example, in the Republic of Ireland it has been estimated that only 0.1% of Covid-19 cases were related to outdoor activities.
It’s not that outdoor contagion is impossible. There are some proven cases. But it requires close and prolonged contact (and it would be minimized by keeping the distance of at least one meter or a meter and a half or using the mask when that distance cannot be maintained).
Additionally, and it is a very relevant aspect, in the open air there will be no “super contagion” events. In one of the few studies that have demonstrated the possibility of outdoor transmission, only one (out of 318 outbreaks) occurred outdoors and was limited to two people.
Vaccination, herd immunity, and severity of disease
“Achieving group immunity” is a very worn phrase, but it makes little sense when you confuse group immunity with a threshold above which you are safe and below you must remain confined. It is simply a parameter used in epidemiology to estimate the proportion of the population to be vaccinated so that transmission begins to decline (so that the basic reproductive index is below unity).
The vaccination strategy followed in Spain (and in Europe) of prioritizing people with the highest risk of developing severe Covid-19 (the elderly) has dissociated transmission data from hospitalizations and deaths. When 81% of the population over 40 years of age has at least one dose and 46% of the full regimen (practically 100% in those over 70 years of age), the impact of transmission will not resemble what we have seen until now.
The foreseeable increase in transmission
The current situation in Spain (still variable according to territories) is characterized by a general reduction in transmission, a notable decrease in hospitalizations and deaths (even in the territories with the highest transmission), and a growing drive for vaccination.
The greatest risks appear to be in outbreaks in young people (under 40 years of age), still unvaccinated, who mostly develop asymptomatic or mild symptoms (which does not exclude the presence of serious cases). Transmission in these people must be greater than what we are capable of detecting in the context of the majority of asymptomatic (difficult to trace) and mild patients, many of whom try to evade the trace or go to the doctor to avoid isolation.
The mobility and social activities of these young people have grown, especially in indoor spaces (hotels, leisure, clubs, homes, face-to-face work). Therefore, transmission, as we already see in other countries, will inevitably grow in these groups. And, of course, the restrictive measures that have been used so far will not have any support in this population, nor – with the current numbers of serious cases – in the rest of the population or in the courts.
Efforts to control transmission in this context go through 3 basic strategies:
case detection, tracing and isolation.
indoor control, with an essential role for cross ventilation that has given such good results in schools, but without neglecting gauges, distances and masks.
What about outdoor masks?
In general they are unnecessary. They will have to be carried over, of course. Use them when entering indoors, on public transport or when you cannot keep your distance (in crowds, which in any case it would be better to avoid, or when talking to someone outside our bubble). Also, obviously, in people with respiratory symptoms or their contacts.
Some of these situations can be monitored. Others require, rather than sanctions, information on when to wear masks outdoors, and civic behaviors. Pandemics are a time to understand that our health is in our hands, but not only in our hands. We also depend on each other. And also of our public health strategies.
The population’s commitment to public health interventions does not seem to depend so much on the normalization of imposed habits as on trust in the decisions that are made and the way in which these decisions are made (information, transparency).
An arbitrary ordinance affects people’s trust in health administrations and harms all public health strategies.
This article was originally published on The Conversation. Read the original.
Salvador Peiró has received funding from national public competitive grants (in general, research or innovation actions -projects, networks, HR, platforms- from the Strategic Action in Health of the National R + D + i Plan) and by institutional agreements with firms pharmaceutical and technological. Funders have never played any role in study design, data acquisition, analysis, or interpretation. They have also not had access to the data sources and never influenced the publication decision. He is also a patron of the Health Services Research Institute Foundation and a member of the Health Economics Association (AES), of the Spanish Epidemiology Society (SEE), of the Spanish Society of Public Health and Health Administration (SESPAS) and the Spanish Society for Healthcare Quality (SECA).