key: cord-0736014-g9tq0yr4
authors: Reeves, Daniel B.; Bracis, Chloe; Swan, David A.; Burns, Eileen; Moore, Mia; Dimitrov, Dobromir; Schiffer, Joshua T.
title: Rapid vaccination and partial lockdown minimizes 4th waves from emerging highly contagious SARS-CoV-2 variants
date: 2021-04-20
journal: Med (N Y)
DOI: 10.1016/j.medj.2021.04.012
sha: ae67314bff459d9a327b83d9c8c1d3385db65242
doc_id: 736014
cord_uid: g9tq0yr4

nan

a publicly available tool https://covidmodeling.fredhutch.org/ which has additional documentation and 23 the ability for the user to see the most up to date projections and explore scenarios.

We modeled a vaccine program beginning in January 2021 that initially prioritized seniors. The initial 25 "Biden plan" of 1m doses per day 2 in the US implied a vaccination rate of ~3500 per day in our model 26 (~7000 doses per day in King County and mostly 2-dose vaccines). Because rates have continuously 27 improved, we modeled 5000 vaccinations per day until Mar 1, 2021 and varied the vaccination rate 28 moving forward at 5000, 10000, or 15000 per day. Vaccination continues until reaching 90% of adults 29 (roughly 75% total coverage because children are not yet vaccinated). To simplify logistics in the model,

we assume that beginning 2 weeks after their second dose, vaccinees are protected.

COVID-19 vaccine efficacy was originally measured as reductions in symptomatic disease 3,4 . Therefore, 32 we assume vaccines can achieve this efficacy by 3 mechanisms: infection is completely blocked 

We also included emerging SARS-CoV-2 variants. We parameterized introduction of the B.1.1.7 variant 37 which is widespread in Europe and present locally with an increased infectivity of 55% relative to 38 dominant US variants 6 , increased mortality of 55% 7 , and a variable importation rate into King County.

While unexpected for B.1.1.7, reduced vaccine efficacy against a new variant was also considered.

Because human behavior and governmental policy (e.g. lockdowns) strongly influence epidemic 41 dynamics, our model directly simulates local policy using a time-and age-varying societal reduction.

lockdown. While we include increased severity of new variant infections, because of vaccine-48 prioritization to elders, deaths are projected substantially lower in the 4 th vs 3 rd wave. Hospitalization Other variables could aid or counteract rapid vaccination (panels in Fig S1C) . While our initial 

While we observe a general relationship between fewer cases, hospitalizations, and deaths with faster 62 vaccination, the interplay with lockdown timing can be important. Cumulative infections were not 63 monotonically improved by vaccination rate in some scenarios because of a complex challenge arising lockdown (while eventually instated) occurs in the next assessment period and thus more infections 66 occur between assessments. However, in those scenarios slower vaccination ultimately required more 67 time at lockdown (see lockdown days in Fig S1C) , emphasizing the additional impact of vaccination on 68 societal health.

Some regions like King County instituted partial lockdown more rapidly during the 3 rd wave, and many of these ideas. DBR gratefully acknowledges the support of the 143 slightly lower such that lockdown (while eventually instated) occurs later and thus ultimately more

COVID-19 vaccines that reduce 10