The risk of the fourth wave for various options of opening schools on May 4

The analysis below examines the possibility of the spreading of wave IV of the epidemic, with different variants of school opening on May 4, 2021, and two alternative virus infectivity values in schools.

Basic information about the analysis.

We analyze two variants of the population immunity level – the cumulative amount of actual infections on March 1 is about 25% or about 33%.
In all scenarios, the vaccination program is considered as follows:
• 700-900 thousand persons monthly vaccinated with the first dose of Comirnata (Pfizer) vaccine in the following order:
• 660 thou. age group 20+
• 2 300 thou. age group 70+
• 1,900 thou. age group 60+

In addition, we include vaccinations with the first dose of AstraZeneca at the level of 830 thou. people per month from February 15 in the 20-65 age group. Assuming a 60% effectiveness of this vaccine, this means 500 thou. monthly “successfully vaccinated” people.

The analysis takes into account:
• 02/27 restrictions in the Warmińsko-Mazurskie voivodeship,
• 03/15 restrictions covering 4 more voivodeships,
• 03/20 extension of restrictions to the whole country, in particular school closure,
• 03/29 closing of kindergartens and most services,
• April 19 opening of kindergartens,
• On April 26, hybrid opening of classes 1-3 in 11 voivodeships.

In the analysis below, we assume full-time school openings, in the following variants:
• Grades 1-3,
• Grades 1-8,
• All schools.

For the purposes of this analysis, we assumed two different levels of infectivity in children and adolescents compared to infectivity in adults: reference and higher. This is an assumption that helps to estimate the possible prediction error due to the degree of infectivity of the British variant among children and adolescents or the hypothetical possibility of the emergence of another, as yet unknown factor that increases infectivity among children and adolescents.

Higher immunization (33% as of March 1):

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Lower immunization (25% as of March 1):

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As can be seen from the above charts, in most cases, the potential for wave IV to open schools is negligible or small. The exceptions are situations in which we assume higher infectivity of the virus among children and lower immunization, or we open all facilities in the country at one time.

For a low level of immunization, the potential of wave IV ranges from 18,000 to 44,000 daily cases reported (depending on the range of school openings). In the case of higher immunization, the risk of wave IV occurs only when all schools are opened.

This is consistent with the fact of having higher immunization in grades 1-3 who were not in remote learning and had a greater chance of contracting the infection and, therefore, acquiring immunity.

With the above assumptions, it can be concluded that the opening of classes 1-8 in May does not carry a high risk of the fourth wave of the epidemic, unless a new, so far unknown factor appears, which will cause higher infectivity of the virus among this age group.