Projected COVID-19 epidemic in the United States in the context of the effectiveness of a potential vaccine and implications for social distancing and face mask use

Abstract

Background Multiple candidates of COVID-19 vaccines have entered Phase III clinical trials in the United States (US). There is growing optimism that social distancing restrictions and face mask requirements could be eased with widespread vaccine adoption soon. Methods We developed a dynamic compartmental model of COVID-19 transmission for the four most severely affected states (New York, Texas, Florida, and California). We evaluated the vaccine effectiveness and coverage required to suppress the COVID-19 epidemic in scenarios when social contact was to return to pre-pandemic levels and face mask use was reduced. Daily and cumulative COVID-19 infection and death cases from 26th January to 15th September 2020 were obtained from the Johns Hopkins University Coronavirus resource center and used for model calibration. Results Without a vaccine (scenario 1), the spread of COVID-19 could be suppressed in these states by maintaining strict social distancing measures and face mask use levels. But relaxing social distancing restrictions to the pre-pandemic level without changing the current face mask use would lead to a new COVID-19 outbreak, resulting in 0.8-4 million infections and 15,000-240,000 deaths across these four states over the next 12 months. Under this circumstance, introducing a vaccine (scenario 2) would partially offset this negative impact even if the vaccine effectiveness and coverage are relatively low. However, if face mask use is reduced by 50% (scenario 3), a vaccine that is only 50% effective (weak vaccine) would require coverage of 55-94% to suppress the epidemic in these states. A vaccine that is 80% effective (moderate vaccine) would only require 32-57% coverage to suppress the epidemic. In contrast, if face mask usage stops completely (scenario 4), a weak vaccine would not suppress the epidemic, and further major outbreaks would occur. A moderate vaccine with coverage of 48-78% or a strong vaccine (100% effective) with coverage of 33-58% would be required to suppress the epidemic. Delaying vaccination rollout for 1-2 months would not substantially alter the epidemic trend if the current non-pharmaceutical interventions are maintained. Conclusions The degree to which the US population can relax social distancing restrictions and face mask use will depend greatly on the effectiveness and coverage of a potential COVID-19 vaccine if future epidemics are to be prevented. Only a highly effective vaccine will enable the US population to return to life as it was before the pandemic.

The Effect of Vaccination Rates on the Infection of COVID-19 under the Vaccination Rate below the Herd Immunity Threshold

“…Only when the accumulated vaccination rate reaches a certain level does partial protection of herd immunity more or less take place, and the infection of disease is reduced. The study of Shen et al [ 12 ] shows that low effective vaccines under low vaccination rates cannot suppress the spread of the COVID-19 pandemic. This paper concludes a similar viewpoint.…”

“…This paper concludes a similar viewpoint. The study of Shen et al [ 12 ] developed a mathematical model to project the spread of the COVID-19 pandemic. It suggests that without using a mask, a 50% effective vaccine will not suppress infection at low vaccination coverage rate, but an 80% effective vaccine requires a 48–78% vaccination coverage rate, and a 100% effective vaccine requires 33–58% vaccination coverage to curb the spread of the COVID-19 pandemic.…”

Modes of transmission of SARS-CoV-2 and evidence for preventive behavioral interventions

“…More realistically, a vaccine with 70% efficacy must be administered to almost 95% of the South African population to contain the epidemic [89]. A model of the United States predicts that if face mask use stops completely, between 33 and 58% of the population would need to be vaccinated with a 100% effective vaccine to suppress the epidemic [90]. This threshold is roughly the same in the realistic scenario where face mask use is reduced by 50% and vaccine effectiveness is 80% [90].…”

“…A model of the United States predicts that if face mask use stops completely, between 33 and 58% of the population would need to be vaccinated with a 100% effective vaccine to suppress the epidemic [90]. This threshold is roughly the same in the realistic scenario where face mask use is reduced by 50% and vaccine effectiveness is 80% [90]. As more research is done to determine the threshold for herd immunity, the sustained implementation of preventive behavioral interventions remains important in preventing ongoing community transmission of SARS-CoV-2.…”

Knowledge and Practice of Health Care Providers Towards Proper Face Mask Utilization to Minimize the Extent of COVID-19 Infection in Amhara Region Referral Hospitals, Ethiopia

“…In resource-constrained countries, the prevalence of communicable diseases is high, and hospitals can rely heavily on face masks to protect medical personnel from coronavirus infection and prevent cross-contamination among patients, the general public, and health care workers. 12 , 13 Different study shows wearing of face mask can reduce the risk of respiratory virus infection. A systematic review and meta-analysis in Chinese show wearing of face mask can prevent from influenza virus and SARS-CoV-2.…”