Covid-19 Simulation Shows The Importance of Safety Product Efforts During Vaccine Distribution

SARS-CoV-2 vaccination can reduce transmission as well as COVID-19 morbidity and mortality[1]. According to recent mathematical modeling, prioritizing the distribution of vaccine and their utilization would maximize the advantages of potentially effective vaccines[2].

According to one study[3], at minimum 75 % of Americans need vaccination with a 70% effectiveness to decrease COVID cases by over 99% without any other non-pharmaceutical interventions(NPIs) - such as face masks and social distancing. Due to the complexity of vaccination on a large scale, its development, distribution, and application, ensuring coverage on a greater scale will be difficult[3].

As a result, critical questions remain about whether NPIs, including face masks and social distancing, should be continued as more and more people are vaccinated[4]. High vaccination coverage and adherence with NPIs are required to avoid COVID-19 outbreaks, admissions to hospitals, and deaths. But most people are unclear about the importance of non-pharmaceutical intervention (NPIs).

A study[5] is carried out in North Carolina evaluated the impacts of varied vaccination coverage and efficacy with and without NPIs maintained and withdrawn simultaneously with vaccine administration. This study found more noticeable variations in new cases with or without NPIs with less coverage and efficacy of the vaccine.

The picture above from the simulation is a model for several North Carolina cases. Keeping in mind that Moderna and Pfizer vaccines have over 90% efficacy to reduce the risk of severe COVID-19. Black, purple and blue lines can be used to see what could happen when the vaccinated communities did not use non-pharmaceutical (NPI) interventions such as mask-wearing and social distancing. Secondly, the simulation highlights the importance of completely vaccinating as many people as possible. For example, in the situation of  A1, there is a continuous drop of cases to very few new COVID cases over six months if 75 % of our population is fully vaccinated and follow NPIs. Compared with C0 with only 25% of our population was vaccinated entirely and did not follow NPIs, there is an apparent increase in daily COVID cases, reaching roughly 8,000 before declining. 

Endpoint:

According to simulation results, removing NPIs while vaccines are being distributed could significantly increase infections, admissions, and mortality. In addition, with the removal of NPIs, greater vaccine coverage with relatively less effective vaccines can result in a greater risk reduction for COVID-19 in comparison with more effective vaccines with less coverage. It is suggested a need for good-coordinated vaccine coverage, mental health well-being, and continued compliance with NPIs, before resuming various pre-pandemic activities.

References: 

1. Jeyanathan, M., Afkhami, S., Smaill, F., Miller, M. S., Lichty, B. D., & Xing, Z. (2020). Immunological considerations for COVID-19 vaccine strategies. Nature Reviews Immunology, 20(10), 615-632.
2. Paltiel, A. D., Schwartz, J. L., Zheng, A., & Walensky, R. P. (2021). Clinical Outcomes Of A COVID-19 Vaccine: Implementation Over Efficacy: The study examines how definitions and thresholds of vaccine efficacy, coupled with different levels of implementation effectiveness and background epidemic severity, translate into outcomes. Health Affairs, 10-1377.
3. Bartsch, S. M., O'Shea, K. J., Ferguson, M. C., Bottazzi, M. E., Wedlock, P. T., Strych, U., ... & Lee, B. Y. (2020). Vaccine efficacy needed for a COVID-19 coronavirus vaccine to prevent or stop an epidemic as the sole intervention. American journal of preventive medicine, 59(4), 493-503.
4. Saad-Roy, C. M., Wagner, C. E., Baker, R. E., Morris, S. E., Farrar, J., Graham, A. L., ... & Grenfell, B. T. (2020). Immune life history, vaccination, and the dynamics of SARS-CoV-2 over the next five years. Science, 370(6518), 811-818.
5. Patel, M. D., Rosenstrom, E., Ivy, J. S., Mayorga, M. E., Keskinocak, P., Boyce, R. M., ... & Swann, J. L. (2021). Association of Simulated COVID-19 Vaccination and Nonpharmaceutical Interventions With Infections, Hospitalizations, and Mortality. JAMA Network Open, 4(6), e2110782-e2110782.