Effects of vaccination and non-pharmaceutical interventions and their lag times on the COVID-19 pandemic: Comparison of eight countries.

Hao Li,Yihan Lu,Mengxi Zhang,Luqi Wang,Weibing Wang,Mohamed Gomaa Kamel

doi:10.1371/journal.pntd.0010101

Abstract

Many countries implemented measures to control the COVID-19 pandemic, but the effects of these measures have varied greatly. We evaluated the effects of different policies, the prevalence of dominant variants (e.g., Delta), and vaccination on the characteristics of the COVID-19 pandemic in eight countries. We quantified the lag times of different non-pharmaceutical interventions (NPIs) and vaccination using a distributed lag non-linear model (DLNM). We also tested whether these lag times were reasonable by analyzing changes in daily cases and the effective reproductive number (Rt)over time. Our results indicated that the response to vaccination in countries with continuous vaccination programs lagged by at least 40 days, and the lag time for a response to NPIs was at least 14 days. A rebound was most likely to occur during the 40 days after the first vaccine dose. We also found that the combination of school closure, workplace closure, restrictions on mass gatherings, and stay-at-home requirements were successful in containing the pandemic. Our results thus demonstrated that vaccination was effective, although some regions were adversely affected by new variants and low vaccination coverage. Importantly, relaxation of NPIs soon after implementation of a vaccination program may lead to a rebound.

Highlights

The coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has spread throughout the world since its initial identification in December 2019, and has had devastating effects in many countries
As of August 31, 2021, Singapore (75.21%), United Kingdom (62.91%), Israel (62.45%), and United States (51.77%) have high shares of the population fully vaccinated against COVID-19, whereas this proportion was relatively low in Australia (27.80%) and India (10.61%) [3]
The results of our distributed lag non-linear model (DLNM) analysis indicated that school closure (C1), workplace closure (C2), restrictions on mass gatherings (C4), and stay-at-home requirements (C6) had the desired protective effects, as indicated by declines in relative risk (RR) in S1–S8 Figs

Summary

Introduction

The coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has spread throughout the world since its initial identification in December 2019, and has had devastating effects in many countries. It has been reported that more than 6000 non-pharmaceutical interventions (NPIs, the most important countermeasures before vaccinations became available) were implemented across 261 countries and territories [2]. Large nationwide COVID-19 vaccination campaigns began worldwide at the beginning of 2021. As of August 31, 2021, Singapore (75.21%), United Kingdom (62.91%), Israel (62.45%), and United States (51.77%) have high shares of the population fully vaccinated against COVID-19, whereas this proportion was relatively low in Australia (27.80%) and India (10.61%) [3]. An observational study in Israel reported that the adjusted estimates of BNT162b2 vaccine effectiveness at 7 days or longer after the second dose was95.3% [4]. A study in England reported that the BNT162b2 vaccine had an effectiveness of 85% at 7 days after the second dose [5]. A study in Chile reported that the estimated vaccine effectiveness of inactived vaccine (CoronaVac) was 65.9% [6]

Methods

Results

Discussion

Conclusion