The summer break effects on the CoViD-19 pandemic in Germany 2020-2022

Jan Lorenz

jlorenz@constructor.university

Constructor University

2023-01-10

Do summer breaks increase or decrease the pandemic?

More technical: Do the reduce or increase the reproductive number?

Both directions possible

☀️️ Summer break

Decreasing

➡️ kids are not in school ➡️ parents take holidays ➡️ cuts off channels of contagion

Increasing

➡️ families travel ➡️ meeting relatives and friends ➡️ new channels of contagion

How can we study which effect is stronger?

Data

Data for regional units in Germany is available through the Robert-Koch-Institut (RKI) at GitHub.

Aggregate new cases per day per federal state.
Seven-day averages to smooth out the typical weekly seasonality of CoViD-19 reporting.
- One data point: Average of new cases of that day and the six days before.

German Trend

German Trend - Summer Period

School summer vacations

German Trend with Summer Breaks

Strategy of analysis:
Compare Trend in federal state during summer break with the German-wide trend.

Idea

Five days delay (incubation period)
Re-scale the German-wide trend
Measure the summerbreak effect 5 days after the end of the summer break

Cases increase more than the German-wide trend.

Two years later

Cases increase less than the German-wide trend.

All federal states in 2020

Vacation more often increase cases

In most federal states case number increased more than the German-wide trend
The relationsships vanishes in 2022 (transition to endemic phase)

Average summer break effect

2020	2021	2022
+46%	+33.3%	+5.45%

Significance of average effect

Year	Mean effect	Lower bound 0.95-CI	p-value
2020	+46%	+13.7%	0.00899
2021	+33.3%	+14.2%	0.00266
2022	+5.45%	-5.13%	0.196

Conclusion: Increasing is stronger

☀️️ Summer break

Decreasing

➡️ kids are not in school ➡️ parents take holidays ➡️ cuts off channels of contagion

Increasing

➡️ families travel ➡️ meeting relatives and friends ➡️ new channels of contagion

Potential reason:
Prevention measures
at school and the at the workplace worked better than
those for leisure activities or when meeting friends and relatives.

Appendix: Additional analyses

All federal states in 2021

All federal states in 2022

No geographic pattern