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The COVID-19 pandemic has taken a heavy toll on human life and the global economy, as well as devastating social and psychological impact due to recurring lockdown situations. Recently launched COVID-19 vaccination programs aim to prevent deaths and reduce spikes in hospitalizations to prevent collapse of health systems. Since many infected people develop serious illness and long-term debilitating symptoms, limiting the cumulative number of cases is a priority.
Another main objective of vaccination is to allow the safe reopening of businesses, schools and public spaces. Prior to the implementation of the vaccination, several strategies such as the use of masks, testing and tracing, and social distancing were in place to prevent an increase in cases and subsequent closures. While these measures have helped control the transmission of the virus, they were insufficient to prevent recurrent waves of infection in many countries.
Another major concern is the emergence of more infectious variants of the virus in many countries such as the UK, Brazil and South Africa. The UK variant or B.1.1.7 variant is believed to be much more contagious and is crushing healthcare systems in the UK and spreading around the world.
While the impact of non-pharmaceutical interventions on newer variants of SARS-CoV-2 is still unclear, these interventions come at a significant cost. School and business closures have a disproportionate impact on people of color and socio-economically backward regions. A key goal of immunization plans should be to limit the intensity and duration of lockdowns this year.
Analyze the complexities of vaccine implementation using mathematical models
Recently, French and American researchers analyzed the complexities of implementing vaccines during the 3rd wave of SARS-CoV-2 infections and potentially future waves, using a mathematical model calibrated on data from King County, Washington. The researchers’ goal was to understand which variables have the greatest impact on infections and mortality to help limit them while decreasing lockdown time. The study is published on the pre-print server withRxiv*.
The model used by the team allows projections in other states with a lower or higher incidence at the time of launching local immunization programs. Researchers simulated various scenarios with different vaccination rates, vaccine efficacy profiles and case thresholds for implementing and relaxing partial locks and speculated that a more contagious variant is currently present at mild levels. .
“Our model projects that with the newer, more infectious variants, higher case thresholds to trigger a partial lockdown will lead to more total infections and deaths per capita.
A high vaccination rate and a low case threshold to trigger a partial lockdown are the main variables for limiting total infections and deaths, regardless of the vaccine efficacy profile. Heatmaps demonstrating the joint effects of vaccination rate (x-axis) and case threshold to trigger partial lockout (y-axis) are presented for four plausible vaccine profiles. a. VESUSC = 90% / VESYMP = 10% / VEINF = 10%, b. VESUSC = 50% / VESYMP = 10% / VEINF = 10%, c. VESUSC = 10% / VESYMP = 90% / VEINF = 10%, d. VESUSC = 10% / VESYMP = 50% / VEINF = 10%. Results are total infections (top row), total number of deaths (middle row), and days of partial lock-out after starting vaccination (bottom row). Increasing the vaccination rate reduces infections and deaths in all scenarios. Increasing the vaccination rate dramatically reduces the total number of lockout days, especially when the case trigger threshold for partial lockout is low. Lowering case thresholds to trigger a partial lockdown decreases the total number of infections and deaths, but results in a higher number of days under partial lockdown in many scenarios. A decrease in VESUSC (a to b) results in more infections and deaths with only a slight impact on lockout time. A decrease in VESYMP (ie) results in more infections and deaths with only a slight impact on lockout time. VESUSC allows a substantial reduction in infections but a slight reduction in deaths compared to an equivalent VESYMP (a to c and c to d).
Increasing vaccination rate decreases the number of cases and deaths, as well as the number of days of isolation
In all scenarios, the new variant quickly became dominant in early summer. Low case thresholds for partial locks during current and future waves strongly predict a lower number of infections, hospitalizations and deaths in 2021. However, there is an expected delay in the onset of a disease. outbreak of new variant infections in locations with relatively higher seroprevalence. For all vaccine efficacy profiles considered in this study, increasing the vaccination rate decreases the number of infections and deaths and the number of days under partial lockout.
“The high efficacy of vaccines against new, more contagious variants, and in particular their ability to block ongoing transmission rather than simply preventing symptoms, will potentially prevent thousands of infections and save hundreds of lives in the world. King County. “
Researchers project significant uncertainty in the timing and intensity of future waves due to varying estimates of the infectivity of new emerging variants, vaccine efficacy against these new variants, vaccine rejection, and adherence. future to masking and social distancing of SARS-CoV-2 infection. Nevertheless, in all the plausible scenarios considered in this work, rapid vaccination and early implementation of lockdown are the most crucial variables that help save the most lives.
“It’s often said that vaccines don’t save lives, vaccinations do. Our modeling strongly reinforces this point.“
*Important Notice
medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behaviors, or treated as established information.
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