Comparison of COVID-19 and seasonal influenza under different intensities of non-pharmaceutical interventions and vaccine effectiveness

Abstract

Background: The COVID-19 pandemic has lasted more than 2 years, and the global epidemic prevention and control situation remains challenging. Scientific decision-making is of great significance to people's production and life as well as the effectiveness of epidemic prevention and control. Therefore, it is all the more important to explore its patterns and put forward countermeasures for the pandemic of respiratory infections.

Methods: Modeling of epidemiological characteristics was conducted based on COVID-19 and influenza characteristics using improved transmission dynamics models to simulate the number of COVID-19 and influenza infections in different scenarios in a hypothetical city of 100,000 people. By comparing the infections of COVID-19 and influenza in different scenarios, the impact of the effectiveness of vaccination and non-pharmaceutical interventions (NPIs) on disease trends can be calculated. We have divided the NPIs into three levels according to the degree of restriction on social activities (including entertainment venues, conventions, offices, restaurants, public transport, etc.), with social controls becoming progressively stricter from level 1 to level 3.

Results: In the simulated scenario where susceptible individuals were vaccinated with three doses of COVID-19 coronaVac vaccine, the peak number of severe cases was 26.57% lower than that in the unvaccinated scenario, and the peak number of infection cases was reduced by 10.16%. In the scenario with level three NPIs, the peak number of severe cases was reduced by 7.79% and 15.43%, and the peak number of infection cases was reduced by 12.67% and 28.28%, respectively, compared with the scenarios with NPIs intensity of level 2 and level 1. For the influenza, the peak number of severe cases in the scenario where the entire population were vaccinated was 89.85%, lower than that in the unvaccinated scenario, and the peak number of infections dropped by 79.89%.

Conclusion: The effectiveness of COVID-19 coronaVac vaccine for preventing severe outcomes is better than preventing infection; for the prevention and control of influenza, we recommend influenza vaccination as a priority over strict NPIs in the long term.

Keywords: COVID-19 pandemic; non-pharmaceutical interventions; seasonal influenza; transmission dynamics model; vaccine.

Figure 1

The transmission chain of transmission dynamics model is constructed according to epidemic characteristics of diseases. The SEIR model includes six compartments, i.e., Susceptible (S), Exposed (E), Mild cases (I₁), Moderate cases (I₂), Severe cases (I₃), and Removed (R).

Figure 2

Changes in numbers of mild, moderate, and severe cases in scenarios 1 (A) and 2 (B). In scenario 1, we assumed no NPIs or vaccination against COVID-19. In scenario 2, we assumed no NPIs and 33% effectiveness of vaccination to prevent infection of COVID-19. The blue, yellow, and red curves represent the number of mild, moderate, and severe cases, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Table 3.

Figure 3

Changes in numbers of mild, moderate, severe cases in scenarios 3 (A), 4 (B), and 5 (C). The blue, yellow, and red curves represent mild, moderate, and severe cases, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Table 3.

Figure 4

Changes in numbers of severe cases and infections in scenarios 1, 2 (A) and scenarios 3, 4, 5 (B). In (A), the red and blue solid curves represent the number of infections in scenarios 1 and 2, respectively. The red and blue dotted curves represent the number of severe cases in scenario 1 and scenario 2, respectively. In (B), the red, blue, and yellow solid curves represent the number of infections in scenario 3, scenario 4, and scenario 5, respectively. The red, blue, and yellow dotted curves represent the number of severe cases in scenario 3, scenario 4, and scenario 5, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Table 3.

Figure 5

Changes in numbers of mild, moderate, and severe cases in scenarios 6 (A) and 7 (B). The blue, yellow, and red solid curves represent the number of mild, moderate, and severe cases, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Table 4.

Figure 6

Changes in numbers of cases of different types in scenarios 8 (A), 9 (B), and 10 (C). The blue, yellow, and red curves represent mild, moderate, and severe cases, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Table 4.

Figure 7

Changes in numbers of severe cases and infections in scenarios 6, 7 (A) and 8, 9, 10 (B). In (A), the red and blue solid curves represent the number of infections in scenarios 6 and 7, respectively. The red and blue dotted curves represent the number of severe cases in scenario 6, scenario 7, respectively. In (B), the red, blue, and yellow solid curves represent the number of infections in scenario 8, scenario 9, scenario 10, respectively. The red, blue, and yellow dotted curves represent the number of severe cases in scenario 8, scenario 9, scenario 10, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Table 4.

Figure 8

Comparison of numbers of infections and severe cases in scenarios 1–5 and scenarios 6–10. (A) is the result of comparison of scenario 1 and scenario 6. (B) is the result of comparison of scenario 2 and scenario 7. (C) is the result of comparison of scenario 3 and scenario 8 (Applies to the Y-axis on the right side). (D) is the result of comparison of scenario 4 and scenario 9. (E) is the result of comparison of scenario 5 and scenario 10. The red and blue solid curves represent the number of infections in scenarios 1–10, respectively. The red and blue dotted curves represent the number of severe cases in scenarios 1–10, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Tables 3, 4.

Figure 9

Comparison of peaks (A) and time to peak (B) of numbers of infections and severe cases in scenarios 1–10. In panel (A), the orange and indigo bars represent the number of infections and severe cases in scenarios 1–10, respectively. In panel (B), the orange and indigo lines represent the time to peak of numbers of infections and severe cases in scenarios 1–10, respectively. Scenarios setting are shown in Table 2. Parameter values used are given in Tables 3, 4.