chuka_lis (chuka_lis) wrote,
chuka_lis
chuka_lis

Рано, рано еще "отменять" меры

К сожалению, в США сейчас активно готовится почва для следующей волны ковида.
Сверху спускается здоровый пофигизм в отношении тестирования и ношения масок у привитых, и ввиду того, что благодаря спаду волн эпидемии и росту количества привитых, случаев ковида стало в разы меньше, чем на пике, противоэпидемические меры где плавно, а где радикально сходят на нет.
Update that fully vaccinated people no longer need to wear a mask or physically distance in any setting, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance
Update that fully vaccinated people can refrain from testing following a known exposure unless they are residents or employees of a correctional or detention facility or a homeless shelter
Refrain from testing before leaving the United States for international travel (unless required by the destination) and refrain from self-quarantine after arriving back in the United States
Refrain from testing following a known exposure, if asymptomatic, with some exceptions for specific settings
Refrain from quarantine following a known exposure if asymptomatic
 Refrain from routine screening testing if feasible
При этом вирус из популяции никуда не делся, да и есть места, где заражаемость и заболеваемость на пике, и новые штаммы плодятся с усиленной скоростью. И ничто не будет мешать им распространяться- при отсутствии противоэпидемических мер. В том числе в странах,  где люди прививаются охотно и сейчас случаев ковида - мало. Модели показывают, что не смотря на привитость, новая волна- это практически неизбежное явление.
Вышел очередной препринт на тему опасности повторения волны ковида: ситуация смоделирована на основе данных вспышек в Манаусе, где, не смотря на "природный" популяционный иммунитет после первого удара эпидемии, новый штамм внес свою лепту в формирование последующей волны с высокими уровнями госпитализации и смертности.
Согласно данным статьи, варианты (штаммы) коронавируса, уже присутствующие в популяции, будут способны через несколько месяцев преодолеть иммунитет, вызванный прививкой, и будут являться причиной новой вспышки- если убрать или пренебречь противоэпидемическими мерами.
У меня есть надежда,, что здравомыслящие люди, все же, будут продолжать, на индивидуальном уровне, соблюдать дистанции, носить маски и поменьше собираться толпами в закрытых помещениях, не смотря на обещанную раздачу розовых слонов от официальных лиц.
The high levels of efficacy against transmission for some of these vaccines makes it feasible to use them to suppress SARS-CoV-2 altogether in regions with high vaccine acceptance. However, viral variants with reduced susceptibility to vaccinal and natural immunity threaten the utility of vaccines, particularly in scenarios where a return to pre-pandemic conditions occurs before the suppression of SARS- CoV-2 transmission.
The emergence of immune-evading variants of SARS-CoV-2 darkens this otherwise rosy picture. A number of newly emerged variants have been demonstrated experimentally to be more capable of infecting cells, spreading between hosts, and/or evading natural immunity, vaccines and therapeutics, comparedto the original wild-type (WT) SARS-CoV-29–11. Once variants emerge within a population, they tend to expand rapidly and deterministically due to natural selection, and dominate the local viral population in a relatively short period of time12. These variants have in a number of cases been associated with more severe disease outbreaks, and some variants have been demonstrated to be less susceptible to certain vaccines9,10,13,14
As public health authorities struggle with the problem of vaccine hesitancy, a strategy of trading away non-pharmaceutical interventions (e.g., mask wearing and social distancing) to incentivize higher vaccine uptake has emerged, both in the United States and elsewhere. A number of public health figures and media outlets have explicitly endorsed or encouraged the removal of restrictions as the vaccine rollout proceeds2,15–17and public health authorities are clearly listening18–21.
Unfortunately, in a situation where vaccine-evading variants are circulating widely within the populationas the vaccine is deployed, evolution and infectious disease dynamics would be expected to play out quite differently. In the presence of a widely deployed vaccine, natural selection will act to enrich for the vaccine-resistant variants. Under conditions of high transmission, witha large pre-existing vaccine-resistant viral population, thiscan lead to a scenariowhere variants substantially reduce vaccine efficacy on a population level.
As of this writing, the United States has vaccinated 46% of its adult population27and vaccines are expected to reach 70% of the adult population by July28. As 25% of the United States population consists of children, and vaccine acceptance among the 12-15 year old population (newly eligible for the vaccine)is expected to be lower than acceptance for adults29,one can roughly estimate that the fraction of the total population vaccinated by July would be around 50%. There are five variants of concern as defined by the CDC present at appreciable frequencies in the United States at present (see Table S1 for details): B.1.427 and B.1.429 with a transmissibility 20% greater than ancestral Wuhan strain (Wuhan-Hu-1, referred to here as “WT”); B.1.1.7 (the “United Kingdom” variant), with a transmissibility ~60% higher than wild type10and vaccine efficacy reduction of ~10% against the Pfizer vaccine30; B.1.351 (the “South African” variant), with a transmissibility ~50% higher than WT31and vaccine efficacy reduction of ~25% against the Pfizer vaccine30; and P.1 (the “Brazilian” variant), with a transmissibility ~100% higher than WT32and a ~32% reduction of immunity induced by WT infection32. As of 4/10/2021, B.1.1.7, B.1.351 and P1 constitute ~60%, 1% and 3.7% of all US infections33(Table S1). There are other variants that have emerged recently, such as B.1.617(the “Indian” variant) that are not yet fully characterized and may emerge as a threat during the timeline examined here, but we have not considered these.
We have used amodel incorporating the dynamics of immune-evading variants to ask the question: “Do the expected levelsof vaccine coveragein the US allow us to return to 4normal without suppressing viral transmission first?”Using aSusceptible-Infected-Recovered (S-I-R)epidemiological model with two or morecompeting variantswithsimulation conditions mirroringthe current situation in the United States, we modeledthe impact of vaccine-evading variants on the course of the COVID-19 pandemic in the presence of vaccines.
We simulated the spread of three existing SARS-CoV-2 variants (B.1.1.7, P.1, and B.1.351) in the US ifthecontact rate (the maximum rate at which infected individuals can spread the infection, as dictated by their interactions with others) isallowed to return to pre-pandemic levels. Assuming a moderate level of vaccine coverage similar to current conditions in the US (50% of the population are initially fully vaccinated), we found that the B.1.1.7 variant will quickly expand and become responsible for nearly all infections (Fig. 1B-C), as it did in the UK10. However, the other two variants, which are more capable of infecting individuals who were vaccinated or have been previously infected with WT virus, will cause a spike of infections months after the return to normal contact levels. If only P.1 and B.1.1.7 are present in the population, P.1 will cause a wave of infections affecting >80% of the population, including those who have beenvaccinated (Fig. 1D). Without P.1, the B.1.351 variant will still cause a wave of infections, although it will occur later and affect fewer individuals (Fig. 1E). Assuming all three variants are initially present in the population (at the frequenciesestimated by the CDC as of 4/10/21), if a full returnto pre-pandemic conditionsis attempted after vaccination, P.1 will become the dominant strain in the US within a matter of months (Fig. 2). This surge in variant infections is predictedto lead to hundreds of millions of COVID-19 cases, as well as millionsof COVID-19 fatalities (Table 1). The predicted fatalities shown in Table 1 were calculated using a base infection fatality rate of 0.68%34(Methods). We also assumed that vaccination results in a 70% reduction in risk of death given infection, which was observed for the Pfizer vaccine for wild-type SARS-CoV-235. Variant infections (notably, P.1) will be responsible for the vast majority of cases and will increase the total infection burden approximately 100-fold (Table 1).These results suggest that, in the presence of vaccine-evading strains, a return to pre-pandemic levels of contactfollowing vaccination is likely to result in unsustainable mortality and morbidity burdens.

In this work we model the situation in the United States at present, to demonstrate how the P.1 variant of SARS-CoV-2 can cause a rebound wave of COVID-19 in a matter of months, similar to what happened in Manaus at the beginning of this year. A high burden of morbidity (and likely mortality) remains possible, even if the vaccine is partially effective against new variants and widely accepted. Our modeling suggests that variants that are already present within the population may be capable of quickly defeating the vaccines as a public health intervention, a fatal flaw in strategies that emphasize rapid reopening before achieving control of SARS-CoV-2.

Tags: коронавирус, статьи, эпидемия
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  • 14 comments

  • Про цинк

    Ученые из Бельгии предположили, что сильные воспалительные реакции, и осложнения от ковида чаще случаются у тех, у кого не хватает цинка. Потому они…

  • Рабочий гуморальный иммунитет

    Немцы провели исследование среди 562 медработников- как там обстоит дело с антителами у тех, кто переболел или привился вакцинами разных компаний- 1…

  • Лечение сывороткой переболевших

    Британцы все никак не могли определиться, помогает ли плазма переболевших ковидом, содержащая антитела, в лечении критических больных ковидом.…