chuka_lis (chuka_lis) wrote,

Актуальность карантинных мер

К вопросу о том, сможет ли привитость снизить распространение вируса и позволит ли отказаться от надоевших масок (и прочих карантинных мер) в ближайшее время.
Вакцина защищает, но не гарантирует что заражения, болезни, передачи вируса не будет- на индивидуальном уровне.
И точно так же- на популяционном. Полезная статья для понимания того, что одни меры только дополняют другие в борьбе с эпидемией, а не заменяют их.
Моделирование показывает, что передачу вируса не удастся свести к 0 до тех пор, пока не будет очень низкая плотность населения, плотные карантинные меры, или 95% привитое населения вакциной, которая обеспечивает 100% защиту от инфекции.
As vaccination efforts to combat the COVID-19 pandemic are ramping up worldwide, there are rising concerns that individuals will begin to eschew nonpharmaceutical interventions for preventing SARS-CoV-2 transmission and attempt to return to pre-pandemic normalcy before vaccine coverage levels effectively mitigate transmission risk. In the U.S.A., some governing bodies have already weakened or repealed guidelines for nonpharmaceutical intervention use, despite a recent spike in national COVID-19 cases and majority population of unvaccinated individuals.
The probability of transmission events occurring was unlikely to reach ≈ 0% outside of scenarios with low population density and multiple nonpharmaceutical interventions, or ≥ 95% vaccine coverage and vaccines that were 100% effective at preventing infections. Given that 1) current estimates place SARS-CoV-2 vaccine efficacies against infection between 60-90% (Hall et al. 2021; Lipsitch & Kahn 2021; Yellen et al. 2021), 2) historical precedence suggesting adult populations will fall well short of these high vaccination levels (Applewhite et al. 2020; CDC 2020), and 3) the difficulty government institutions have had enforcing nonpharmaceutical intervention policies (Jacobs & Ohinmaa 2020; Pedersen & Favero 2020), it is unlikely that these scenarios will be representative of average real-world gatherings. Moreover, in 60-min gathering scenarios, the probability of ≥ 1 successful transmission event occurring is relatively high even when gathering attendees utilize nonpharmaceutical interventions and most are vaccinated.
The probability that ≥1 SARS-CoV-2-positive individual is in attendance at a gathering can be calculated as Embedded Image where p is the local COVID-19 prevalence, and n is the number of people at the gathering (Chande et al. 2020). The prevalence of infectious cases (p) can be highly uncertain because of the variable testing effort across time and space, but it can be estimated by assuming that any SARS-CoV-2-positive individuals are infectious at time of testing and will remain infectious for a given period of time. Additionally, ascertainment bias can be factored in. The probability that a given individual will be infected at a gathering is then Embedded Image where qi is the probability that individual i will be infected given exposure to an asymptomatic individual at the gathering.
Our findings suggest that cloth-based mask use, with or without 2-m social distancing, often does not confer significant protective effects during long-duration gatherings (Fig. 2), we have also shown that implementing these nonpharmaceutical interventions can reduce overall transmission probability (Fig. 1) and secondary attack rates (Fig. 2, Table 3) during brief interactions or gatherings with relatively-few people (e.g., fewer than 10 people, the limit for indoor and/or outdoor social gatherings enforced by some U.S. states (MultiState 2021)). This effectively means that strict guidelines for continued nonpharmaceutical intervention use will likely help to mitigate SARS-CoV-2 spread, and therefore COVID-19 incidence, for as long as these policies are in effect.
Assuming mean population-level vaccine efficacies of 60% and 80%, which we believe are conservative estimates for U.S.-approved vaccine efficacies, our regression model consistently predicts that secondary attack rates decrease by 55-58% when attendees utilize cloth masks and 2-m social distancing, regardless of gathering duration (Fig. 3). However, it is important to reiterate that here we estimate the probability or infection given contact with an infectious individual at a gathering (qi) and comment on the relative risk difference attributable to intervention use.
..the relative impact of nonpharmaceutical interventions on infection risk reduction will likely decrease over time as vaccine rollouts continue.
We found that nonpharmaceutical interventions will often reduce secondary attack rates, especially during brief interactions, and therefore there is no definitive vaccination coverage level that makes nonpharmaceutical interventions completely redundant. However, the beneficial effect on absolute SARS-CoV-2 infection risk reduction conferred by nonpharmaceutical interventions used during indoor gatherings is likely proportional to COVID-19 prevalence.
Therefore, if U.S. COVID-19 prevalence decreases in the future, nonpharmaceutical interventions will likely still confer protective effects
Tags: коронавирус, статьи, эпидемия

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