No local cases for 253 days in Taiwan without strict lockdown or school closure—how?
Comparison of Estimated Effectiveness of Case-Based and Population-Based Interventions on COVID-19 Containment in Taiwan
Taiwan has one of the lowest per capita incidence and mortality rates in the world. This comparative effectiveness study used a stochastic branching process model using COVID-19 epidemic data from Taiwan, an island nation of 23.6 million people, with no locally acquired cases of COVID-19 reported for 253 days between April and December 2020. In our estimated analysis, case detection, contact tracing, and 14-day quarantine of close contacts (regardless of symptoms) was estimated to decrease the reproduction number from the counterfactual value of 2.50 to 1.53 (95% CrI, 1.50-1.57), which would not be sufficient for epidemic control, which requires a value of less than 1. In our estimated analysis, voluntary population-based interventions, if used alone, were estimated to have reduced the reproduction number to 1.30 (95% CrI, 1.03-1.58). Combined case-based and population-based interventions were estimated to reduce the reproduction number to below unity (0.85; 95% CrI, 0.78-0.89). In this comparative effectiveness research study, the combination of case-based and population-based interventions (with wide adherence) may explain the success of COVID-19 control in Taiwan in 2020. Either category of interventions alone would have been insufficient, even in a country with an effective public health system and comprehensive contact tracing program.
The risk of symptomatic reinfection during the second COVID-19 wave in individuals previously exposed to SARS-CoV-2
[Preprint.] In this cohort study, we analyzed surveillance records of COVID-19 cases identified between June 2020 and January 2021 in five Italian municipalities, where 77.7% of the entire population was screened for IgG antibodies in May 2020. We compared the risk of observing symptomatic infections in two mutually exclusive groups defined by the initial serological response. We estimated that the cumulative incidence of identified symptomatic infections in the IgG negative and positive cohorts was 2.67% (95%CI: 2.12% – 3.37%) and 0.14% (95%CI: 0.04% – 0.58%), respectively. The adjusted odd ratio of developing symptomatic infection in individuals previously exposed to SARS-CoV-2 was estimated at 0.054 (95%CI: 0.009 - 0.169).
BNT162b2 Vaccination Effectively Prevents the Rapid Rise of SARS-CoV-2 Variant B.1.1.7 in high risk populations in Israel [Pfizer]
We analyze data from ∼300,000 RT-PCR samples collected from December 6th 2020 to February 10th 2021. We reveal that the B.1.1.7 is 45% (95% CI:20-60%) more transmissible than the wild-type strain, and become the dominant in Israel within 3.5 weeks. Despite the rapid increase in viral spread, focused RT-PCR testing and prioritized vaccination programs are capable of preventing the spread of the B.1.1.7 variant in the elderly.
COVID-19 dynamics after a national immunization program in Israel
In this study, we conducted a retrospective analysis of data from the Israeli Ministry of Health collected between 28 August 2020 and 24 February 2021. we performed several comparisons: (1) individuals aged 60 years and older prioritized to receive the vaccine first versus younger age groups; (2) the January lockdown versus the September lockdown; and (3) early-vaccinated versus late-vaccinated cities. A larger and earlier decrease in COVID-19 cases and hospitalization was observed in individuals older than 60 years, followed by younger age groups, by the order of vaccination prioritization. This pattern was not observed in the previous lockdown and was more pronounced in early-vaccinated cities. Our analysis demonstrates the real-life effect of a national vaccination campaign on the pandemic dynamics.
COVID-19 Outbreak Associated with a SARS-CoV-2 R.1 Lineage Variant in a Skilled Nursing Facility After Vaccination Program — Kentucky, March 2021
In a COVID-19 outbreak at a Kentucky skilled nursing facility involving a newly introduced variant to the region, unvaccinated residents and health care personnel (HCP) had 3.0 and 4.1 times the risk of infection as did vaccinated residents and HCP. Vaccine was 86.5% protective against symptomatic illness among residents and 87.1% protective among HCP.