Capture d’écran 2021-12-31 à 10.43.22

Measures in Schools

Joint statement from the Swiss National COVID-19 Science Task Force, Pédiatrie Suisse and Kinderärzte Schweiz


The SARS-CoV-2 Delta variant has caused an unprecedented surge in infections in the pediatric population. This is most likely related to the increased affinity of the Delta variant for the ACE-2 receptor[1], thereby increasing susceptibility to infection, especially in unvaccinated populations such as children. Another likely contributor is an increased viral load of the Delta variant when compared to previous variants/strains[2], increasing contagiousness of infected persons. In this context, children are not only more susceptible to SARS-CoV-2 infection but also likely more contagious than previously, explaining the sustained circulation in children. Finally, the relaxation of non-pharmaceutical interventions as a consequence of adults being largely vaccinated has allowed a more rapid spread in unvaccinated populations, including children. The Omicron variant, which is now dominant in Switzerland and elsewhere, is much more transmissible than the Delta variant in adults[3]. Even though there is no pediatric-specific data yet, the fact that children are the least vaccinated group will likely be associated with an even more sustained virus circulation in children.

Given the current circumstances, the Swiss National COVID-19 Science Task Force (STF), Pédiatrie Suisse (PS) and Kinderärzte Schweiz (KIS) decided to develop and publish a joint statement regarding measures in schools.

As a foreword to the current statement, a few points should be addressed:

  • STF, PS, and KIS uniformly agree that keeping schools open remains the main goal, in order to limit disruption in children’s education and social contacts.
  • Despite early fears that the Delta variant may cause more severe acute disease, this has not been observed in children[4], the increase in hospitalization being mainly due to the absolute number of children infected. It is yet unclear whether the Omicron variant is associated with a different disease severity in children than previously circulating variants.
  • Given the contagiousness of circulating variants, all children will eventually come into contact with the virus. All unvaccinated children and many vaccinated children will in due course be infected, and for unvaccinated children this will take place without previously trained specific immunity. It is therefore important that measures are in place in schools to limit virus circulation. Such measures  can limit the number of pediatric infections, thus increasing the chances that children whose parents wish to vaccinate them have the opportunity to receive two doses before coming into contact with the virus.

To ensure SARS-CoV-2 circulation remains low in children over the Delta and Omicron waves while keeping schools open and allowing the rollout of vaccination, the STF, PS, and KIS agree on a series of measures detailed below.

1. Air quality/CO2 sensors

Adequate ventilation has been recognized as an important factor in preventing transmission of SARS-CoV-2 through aerosols[5]. This is because ventilation dilutes the concentration of aerosols in the air, and thus reduces the amount of viruses in the air when an infectious individual is present in a room. Consistently ventilating classrooms and other indoor environments in schools is an important means to curb aerosol-based transmission, and even more so when pupils engage in high-aerosol-emission activities (speaking loudly, singing, laughing, carrying out strenuous physical activities). Where mechanical means of air exchange are available, these should be set so that the input of fresh air from outside is maximal, to ensure the greatest dilution of any viruses in the indoor environment. When ventilation is natural (opening windows), this should be done appropriately and consistently. Adequate ventilation is of primary importance in the colder season, when more activities occur indoors. Unfortunately, this is also the time when natural ventilation is most difficult to implement consistently, because of the discomfort associated with opening windows in cold weather.

CO2 monitors can aid in guiding ventilation protocols: by measuring CO2 as a proxy for the air quality in a room, they alert the user to the need to open windows. The use of CO2 monitors removes the subjectivity inherent in ventilating a room by opening windows, preventing ventilation from being insufficient (which increases transmission risk) but also from being excessive (which increases thermal discomfort in colder seasons, ultimately resulting in lower acceptance of ventilation). CO2 monitors do not directly provide a measure of transmission risk, and in selected situations their application requires care[5]. However in the vast majority of situations they are a simple, inexpensive aid to ensure the air quality in a room is good and aerosol-based transmission risk is kept low. Moreover, they might also contribute to reducing transmission of other respiratory pathogens in educational settings. However, it is important to remember that whilst ventilation by itself will reduce the probability of transmission, it will not prevent transmission, for example because individuals spending time close to each other can infect each other through droplets, even when the air quality is good (i.e., CO2 values are low). Particularly when the incidence is high, the wearing of masks should be considered, even in well-ventilated environments.

2. Regular repeated testing of asymptomatic children

In controlled research settings, the early detection of SARS-CoV-2 infection in asymptomatic or mildly symptomatic children through regular repeated testing in schools has been shown to interrupt transmission chains and reduce the overall number of COVID-19 cases in a class/school[6], thereby reducing the likelihood of class/school closure and disruption in education. To be efficient, however, repeated testing should be performed on a regular basis (at least once a week, ideally twice a week) and involve as many children as possible in a class (ideally all). Indeed, given the fact that participation of schools, classes or even individual persons is voluntary, the efficiency of regular repeated testing is directly related to the proportion of children who participate in a given class/school. As long as regular repeated testing contributes to maintaining classes/schools open, it should be supported. It is important to note that the relevance of regular repeated testing must be taken into the epidemiological context. In case of a more sustained SARS-CoV-2 circulation, additional measures should be implemented, such as wearing well-fitted masks in classes and increasing testing frequency.  

3. Approach to symptomatic children

Since March 2021, the Federal Office of Public Health recommends testing of persons 6 years and older in case of any symptom compatible with COVID-19, regardless of the history of contact with an infected case, the general condition, number, type, and duration of symptoms [7]. For children <6 years, criteria are more restrictive, with testing recommended only in the following situations and after evaluation by a physician: 1) fever or strong cough, associated with alteration in the general condition; 2) fever or strong cough, associated with other symptoms compatible with COVID-19; 3) any COVID-19 symptom and contact with a confirmed case of COVID-19. The rationale to limit tests in younger children was based on the following points. First, common respiratory viral infections are very frequent in young children and cannot be clinically distinguished from COVID-19. Hence, wide testing criteria would frequently result in unnecessary swabbing of children, a procedure which is not well-accepted in this age group and is costly. Second, with the wild-type SARS-CoV-2, children were not efficient contributors to SARS-CoV-2 transmission. However, with the new variants, children are more susceptible to infection, explaining in part the current sustained circulation of SARS-CoV-2 in children. Therefore, in this period of high circulation, it remains very important that symptomatic children stay at home regardless of the viral etiology. Ensuring that symptomatic children remain at home will not only interrupt transmission chains of SARS-CoV-2, but also that of the more virulent respiratory viruses such as RSV and Influenza and will also decreases the likelihood of class/school closures and pressure on pediatric hospitals. Since keeping children at home not only disrupts education but may also generate a major psychosocial burden, wider access to testing for symptomatic children <6 years in some circumstances (daycare, unvaccinated parents, contact with vulnerable adults) and after evaluation by a pediatrician would certainly help by allowing an early return to school for children with a negative RT-PCR, especially in the current epidemiological setting.

Regarding testing modality, nasopharyngeal RT-PCR remains the gold standard but the procedure is not well accepted in the pediatric setting. With a sensitivity >90% when compared to nasopharyngeal RT-PCR[8],[9], saliva RT-PCR should be more widely proposed as an alternative because of its ease to perform and its acceptability among children (and parents). Furthermore, a testing modality which is more acceptable would certainly increase the number of children who are tested and consequently the number of identified SARS-CoV-2 infections, a public health benefit possibly outweighing the slightly lower sensitivity of saliva RT-PCR. As rapid antigen tests have not been shown to be sensitive enough in either symptomatic or asymptomatic children [10], regardless of the anatomical site (nasopharynx, oropharynx, nose, saliva), RT-PCR should be preferentially used. Finally, when testing facilities for children are not easily accessible, such as in rural areas, the use of self-tests for symptomatic children could be incentivized, where only children testing positive to a home test would be recommended to get tested in a testing facility.

4. Vaccination for children

mRNA vaccines have been shown to be safe and immunogenic in children 5-11 years old and adolescents 12-17 years old with a respective vaccine efficacy of 91% and 100%, respectively, for symptomatic disease in pivotal clinical trials[11],[12]. Data on asymptomatic infection are not available for the 5-11 years old, but have been shown to be as low as 39% in the 12-17[13]. Despite mutations favoring immune escape in the Delta variant, vaccine efficacy against symptomatic disease caused by the Delta variant remains high at 93% in 12-17 year olds, for example[14]. There are, as yet, no pediatric data about vaccine protection against the Omicron variant. Since the SwissMedic approval of the Pfizer-BNT162b2 vaccine in 12-15 years old on June 4th, 2021, 43% of the Swiss population aged 12-15 has been received two doses ([15]; as per 22.12.2021) and all 12-15 year olds who were willing to be vaccinated have had the opportunity to do so. On December 10th 2021, SwissMedic approved the Pfizer-BNT162b2 vaccine for 5-11 years old [16] with vaccine rollout in this age group expected to start as soon as the first week of January 2022.

The Federal Commission for Vaccination recommends universal immunization of the 12-17 years old. Since December 14th,2021, the Federal Commission for Vaccination also recommends the immunization of the 5-11 years old whose parents wish to do so, especially those with chronic illnesses or those in contact with vulnerable people[17]. Even though vaccinating children can contribute to improving the overall epidemic situation, the decision to vaccinate a child or a teenager should be based on the individual benefit. Besides avoiding the above-mentioned disruptions in education and the associated psychological burden, the vaccine is also expected to reduce pediatric complications of COVID-19. Indeed, as vaccination has been shown to prevent the rare (estimated incidence <0.1%) but severe multisystem inflammatory syndrome associated with COVID-19 (MIS-C) in the 12-18 years old[18], one can expect the same benefits in vaccinated 5-11 years old, the age group with the highest MIS-C incidence[19]. Similarly, as data have shown reduced odds of long-COVID-19 in vaccinated adults[20], one can possibly expect the same benefit in the 5-11 years old, an age category in which long-COVID-19 is less frequent, with an estimated incidence of 0.5-2%.

It is difficult to anticipate how the vaccine for the 5-11 years old will be accepted by the Swiss population, but it is of importance that the vaccine rollout is ready and rapid for 5-11 years old children. For the proportion of the population willing to vaccinate their children, the more quickly children are vaccinated the faster this will contribute to limit virus circulation among children and the consequent disruption of children’s life.

5. Extending school holidays

Given the fact that almost 40% of SARS-CoV-2 infections are diagnosed in the age group 0-19 years old and that circulation of the virus in educational settings is particularly sustained, extending end-of-year school closures both before and after has been proposed by some experts, especially if the omicron variant turns out to increase the burden of disease in children. Given the suboptimal overall vaccine coverage in the country, however, extending school closures would only make sense if they were either part of more general similar measures in the adult population to curb the current epidemic, which would very likely include a drastic restriction of mobility of the entire population, or as part of a more general strategy to implement more protective measures in schools themselves as outlined in this document.


[1] Motozono C, Toyoda M, Zahradnik J, et al. SARS-CoV-2 spike L452R variant evades cellular immunity and increases infectivity. Cell Host Microbe 2021;29 (7):1124-36.e11. doi:10.1016/j.chom.2021.06.006

[2] Li B, Deng A, Li K, et al. Viral infection and transmission in a large, well-traced outbreak caused by the SARS-CoV-2 Delta variant. medRxiv 2021. doi:10.1101/2021.07.07.21260122

[3] Abdool Karim SS, Abdool Karim Q. Omicron SARS-CoV-2 variant: a new chapter in the COVID-19 pandemic. Lancet 2021;398(10317):2126-2128 (10317):2126-8. doi:10.1016/S0140-6736(21)02758-6

[4] Delahoy MJ, Ujamaa D, Whitaker M, et al. Hospitalizations Associated with COVID-19 Among Children and Adolescents – COVID-NET, 14 States, March 1, 2020-August 14, 2021. MMWR Morb Mortal Wkly Rep 2021;70 (36):1255-60. doi:10.15585/mmwr.mm7036e2

[5] Swiss National COVID-19 Science Task Force. On the use of CO2 sensors in schools and other indoor environments. 2021.

[6] Torneri A, Willem L, Colizza V, et al. Controlling SARS-CoV-2 in schools using repetitive testing strategies. 2021. doi:10.1101/2021.11.15.21266187

[7] Bundesamt für Gesundheit BAG. COVID-19 – Empfehlung zum Vorgehen bei symptomatischen Kindern unter 6 Jahren und ande- ren Personen, die Schulen und schul- und familienergänzende Betreuungseinrichtungen fre- quentieren sowie Testindikationen für Kinder unter 6 Jahren. 2021.

[8] Fougère Y, Schwob JM, Miauton A, et al. Performance of RT-PCR on Saliva Specimens Compared With Nasopharyngeal Swabs for the Detection of SARS-CoV-2 in Children: Eine prospektive vergleichende klinische Studie. Pediatr Infect Dis J 2021;40 (8):e300-e4. doi:10.1097/INF.0000000000003198

[9] Huber M, Schreiber PW, Scheier T, et al. High Efficacy of Saliva in Detecting SARS-CoV-2 by RT-PCR in Adults and Children. Microorganisms 2021;9 (3):642. doi:10.3390/microorganisms9030642

[10] L’Huillier AG, Lacour M, Sadiku D, et al. Diagnostic Accuracy of SARS-CoV-2 Rapid Antigen Detection Testing in Symptomatic and Asymptomatic Children in the Clinical Setting. J Clin Microbiol 2021;59 (9):e0099121. doi:10.1128/JCM.00991-21

[11] Walter EB, Talaat KR, Sabharwal C, et al. Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age. N Engl J Med 2021. doi:10.1056/NEJMoa2116298

[12] Frenck RW, Jr., Klein NP, Kitchin N, et al. Safety, Immunogenicity, and Efficacy of the BNT162b2 Covid-19 Vaccine in Adolescents. N Engl J Med 2021;385 (3):239-50. doi:10.1056/NEJMoa2107456

[13] Ali K, Berman G, Zhou H, et al. Evaluation of mRNA-1273 SARS-CoV-2 Vaccine in Adolescents. N Engl J Med 2021;385 (24):2241-51. doi:10.1056/NEJMoa2109522

[14] Reis BY, Barda N, Leshchinsky M, et al. Effectiveness of BNT162b2 Vaccine against Delta Variant in Adolescents. N Engl J Med 2021;385 (22):2101-3. doi:10.1056/NEJMc2114290

[15] Bundesamt für Gesundheit. COVID-19-Impfung. 2021.

[16] Swissmedic. Swissmedic approves COVID-19 vaccine from Pfizer/BioNTech for children aged 5 to 11 years. 2021.

[17] Federal Commission For Vaccination. COVID-19: vaccination recommended and possible for children from the beginning of January. 2021.

[18] Levy M, Recher M, Hubert H, et al. Multisystem Inflammatory Syndrome in Children by COVID-19 Vaccination Status of Adolescents in France. JAMA 2021. doi:10.1001/jama.2021.23262

[19] Payne AB, Gilani Z, Godfred-Cato S, et al. Incidence of Multisystem Inflammatory Syndrome in Children Among US Persons Infected With SARS-CoV-2. JAMA Netw Open 2021;4 (6):e2116420. doi:10.1001/jamanetworkopen.2021.16420

[20] Antonelli M, Penfold RS, Merino J, et al. Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID Symptom Study app: a prospective, community-based, nested, case-control study. Lancet Infect Dis 2021. doi:10.1016/S1473-3099(21)00460-6

As the Swiss National COVID-19 Science Task Force has been disbanded as of 31 March 2022, no further epidemiological assessments, scientific updates or policy briefs will be published in the future. All previous publications, pages and information of the Science Task Force remain available on this website.