School reopenings in many countries have generated questions about the risk of students and staff to COVID-19 and other respiratory diseases. 2021 has seen a number of studies investigating the relationship between schools, interventions to prevent COVID-19, and infection rates in children. Since younger children are not currently eligible to receive vaccination for COVID-19 in some countries, they are especially at risk of infection with SARS-CoV-2 and developing COVID-19. 

Risks associated with school closures

Prolonged school closures are associated with a number of negative outcomes for children. 

The WHO (2020) states that there are risks of a reversal in educational gains, limiting future educational opportunities, potential social and emotional issues for children, and delayed development. School closures can interrupt essential school based services, such as feeding and nutrition, immunization, and mental health support. 

Infection risk of children

Children are well known to be susceptible to a range of common respiratory infections, such as influenza, rhinovirus, and common coronaviruses. When unvaccinated, they are highly susceptible to more serious respiratory diseases such as measles, mumps, and pertussis (whooping cough).  

From the start of the COVID-19 pandemic, children were reportedly infected with SARS-CoV-2 at lower rates than adults, with younger children (0-11) infected at even lower rates than older children (12-18). Because many countries closed schools during the first phases of the pandemic, it was not clear whether lower infection rates in children were because children were less susceptible to SARS-CoV-2 infection or whether being quarantined at home interrupted normal routes of transmission for children associated with schools. 

Early studies showed that most (52%) children that do get infected with SARS-COV-2 are likely infected by a family member (Zachariah, 2020). Children also appear more likely to develop milder disease, but they can become severely ill and die, however this is rare. Globally the WHO estimates (2020) that children comprise 8.5% of all reported COVID-19 cases with fewer reports of severe disease or death. 

In a 2020 study, Heald-Sargent (2020) tested for SARS-CoV-2 in nasopharyngeal swabs and found that children 5-17 had comparable viral loads to adults, but that children <5 years old tended to have higher viral loads. This demonstrates that children of all ages can transmit the virus and younger children may be able to more readily transmit the virus even if they are less likely to become seriously ill or die from the infection. 

Recent studies on children and COVID-19

From early in 2021, the Delta variant of SARS-CoV-2 has concerned medical and public health professionals as the variant appeared to be more transmissible. Several waves of cases were seen across many countries during Jan-Sept 2021. As students returned to in-person instruction in many countries, there was significant interest in whether COVID-19 rates in children would rise and whether the WHO/US-CDC/eCDC recommended safety practices would show enough of a protective effect for students and staff. 

As younger children (5-12 years) cannot currently be vaccinated in most countries, protection for children is provided by those around them following the recommended public health protective practices, most importantly adult and adolescent vaccination, where available. The public health practices recommended by the WHO/US-CDC/eCDC are even more important in environments where vaccination for adults is either low or not available. 

Havers (2021) found that among 204 adolescents hospitalized in 2021 in the US between Jan 1 and Mar 31, 31.4% required treatment in the Intensive Care Unit and 4.9% required mechanical ventilation. Hospitalization rates were lower for adolescents than for adults during this period, but severe disease does occur in adolescents, including the need for mechanical ventilation.

Yin (2021) investigated the impact of the US-CDC recommended COVID-19 prevention practices for in-person instruction on COVID-19 rates in students in LA County in California. The recommended practices included symptom screening, masking, physical distancing, cohorting, and contact tracing. The COVID-19 rates for children and adolescents during the study period were 3.4 times lower than rates in the community during the same time period. This study demonstrates that the recommended public health practices can provide a safer educational environment.

Immune deficit/debt:

“Immunity Debt” is a term used to describe a person not developing immunity to other infections because of observing precautions during the COVID pandemic (Guardian, 2021). A recent commentary in Infectious Diseases Now (Cohen, 2021) voiced the growing concern that this phenomenon is occurring in younger children due to missing substantial time in the classroom, where they are commonly exposed to a wide range of respiratory viruses, such as Respiratory Syncytial Virus (RSV), influenza, and the common coronaviruses. 

As childhood infection rates of these viruses dropped significantly during the lockdown phases of the pandemic, returning to normal levels of activity may not increase the prevalence of these diseases to pre-pandemic levels, but may contribute to a spike in cases above current levels. 

Avoiding “COVID Tunnel Vision” by including hand and surface hygiene

Other pathogens that can cause respiratory disease in children include RSV, influenza, enteroviruses, rhinovirus, and the common coronaviruses. Included in the recommended public health practices to prevent COVID-19 is guidance to routinely perform hand hygiene and to clean and disinfect surfaces. Since hands are most commonly contaminated by touching surfaces (fomites) contaminated with pathogenic organisms, hand and surface hygiene works symbiotically. 

The  “Swiss cheese” model of prevention proposes using a layered approach, including both highly effective and less effective practices, to provide a reasonable amount of protection that doesn’t rely on a single intervention to provide protection. 

Hand and surface hygiene should include routine washing of hands with soap and water, the use of alcohol based hand rubs between hand washing, and routine cleaning and disinfection of commonly touched or higher risk surfaces. Because some respiratory pathogens are small non-enveloped viruses, alcohol based hand rub and surface disinfectants should either carry a full virucidal claim or have data against a range of small, non-enveloped respiratory viruses.

Attending schools in person is important for the social and educational development of children. The COVID-19 pandemic forced school closings in many areas, causing hardships for students and their families. As schools return to normal schedules, several studies have demonstrated that in-person education can be done safely as long as the recommended public health practices are closely followed.