scholarly journals Herd immunity thresholds for SARS-CoV-2 estimated from unfolding epidemics

2020 ◽  
Author(s):  
Ricardo Aguas ◽  
Rodrigo M. Corder ◽  
Jessica G. King ◽  
Guilherme Gonçalves ◽  
Marcelo U. Ferreira ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Individual Variation ◽  
Herd Immunity ◽  
Epidemiological Models ◽  
Classical Formula ◽  
Social Distancing ◽  
Individual Susceptibility ◽  
Reproduction Numbers ◽  
Selective Depletion

As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads, the susceptible subpopulation declines causing the rate at which new infections occur to slow down. Variation in individual susceptibility or exposure to infection exacerbates this effect. Individuals that are more susceptible or more exposed tend to be infected and removed from the susceptible subpopulation earlier. This selective depletion of susceptibles intensifies the deceleration in incidence. Eventually, susceptible numbers become low enough to prevent epidemic growth or, in other words, the herd immunity threshold is reached. Here we fit epidemiological models with inbuilt distributions of susceptibility or exposure to SARS-CoV-2 outbreaks to estimate basic reproduction numbers (R0) alongside coefficients of individual variation (CV) and the effects of containment strategies. Herd immunity thresholds are then calculated as 1 − (1/R0)1/(1+CV2) or 1 − (1/R0)1/(1+2CV2), depending on whether variation is on susceptibility or exposure. Our inferences result in herd immunity thresholds around 10-20%, considerably lower than the minimum coverage needed to interrupt transmission by random vaccination, which for R0 higher than 2.5 is estimated above 60%. We emphasize that the classical formula, 1 − 1/R0, remains applicable to describe herd immunity thresholds for random vaccination, but not for immunity induced by infection which is naturally selective. These findings have profound consequences for the governance of the current pandemic given that some populations may be close to achieving herd immunity despite being under more or less strict social distancing measures.

scholarly journals Individual variation in susceptibility or exposure to SARS-CoV-2 lowers the herd immunity threshold

2020 ◽  
Author(s):  
M. Gabriela M. Gomes ◽  
Ricardo Aguas ◽  
Rodrigo M. Corder ◽  
Jessica G. King ◽  
Kate E. Langwig ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Individual Variation ◽  
Herd Immunity ◽  
Risk Of Infection ◽  
Individual Susceptibility

AbstractAs severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads, the susceptible subpopulation is depleted causing the rate at which new cases occur to decline. Variation in individual susceptibility or exposure to infection exacerbates this effect. Individuals that are frailer, and therefore more susceptible or more exposed, have higher probabilities of being infected, depleting the susceptible subpopulation of those who are at higher risk of infection, and thus intensifying the deceleration in occurrence of new cases. Eventually, susceptible numbers become low enough to prevent epidemic growth or, in other words, herd immunity is attained. Although estimates vary, it is currently believed that herd immunity to SARS-CoV-2 requires 60–70% of the population to be immune. Here we show that variation in susceptibility or exposure to infection can reduce these estimates. Achieving accurate estimates of heterogeneity for SARS-CoV-2 is therefore of paramount importance in controlling the COVID-19 pandemic.

scholarly journals Defining and Computing Reproduction Numbers to Monitor the Outbreak of Covid-19 or Other Epidemics

2021 ◽  
Author(s):  
Paulo Zingano ◽  
Janaina Zingano ◽  
Alessandra Silva ◽  
Carolina Zingano
Keyword(s):  
Evolution Equations ◽  
Herd Immunity ◽  
Epidemiological Models ◽  
Seir Model ◽  
Full Implementation ◽  
Intervention Measures ◽  
Reproduction Numbers

We present a general approach to define reproduction ratios or numbers to monitor the outbreak of epidemics that are modeled by mathematical evolution equations. This provides a solution to an important topic that has not been completely settled in the literature, especially in the case of complex epidemiological models. We illustrate our procedure with a full implementation of a standard deterministic SEIR model that is applied to examine the Covid-19 outbreaks and the effects of intervention measures in several countries in America (Argentina, Brazil, Mexico, USA) and Europe (France, Italy, Spain and UK) in 2020. Our code is also used to investigate herd immunity levels for Covid-19, indicating values between 85% and 90%.

COVID-19: Are Experimental Drugs Cure or Ill?

2021 ◽  
Vol 16 ◽  
Author(s):  
Bensu Karahalil ◽  
Aylin Elkama
Keyword(s):  
Clinical Trials ◽  
Severe Acute Respiratory Syndrome ◽  
Adverse Effects ◽  
Antiviral Treatment ◽  
Herd Immunity ◽  
Mortality Rates ◽  
Death Rates ◽  
Experimental Drugs ◽  
Combined Use ◽  
The World

Background: Coronavirus disease 2019 (COVID-19) is a new strain of coronavirus. It is characterized by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has quickly influenced all over the world since it spreads easily. Common symptoms are fever, cough, difficulty in breathing and muscle aches. Despite the urgent need to find an effective antiviral treatment, already available agents are being used alone or in combination all over the world. At the beginning of the pandemic, death rates of infection caused by COVID-19 are high but "is COVID-19 responsible for all deaths?", or “are there any contributions of the frequently used drugs in this period to these deaths?” Surely herd immunity plays a major role and has the contribution in the decline in mortality rates. Meanwhile, it is kept in mind that due to safety concerns, changes have also been made to the dosage and combined use of frequently used drugs. Objective: In this review, answers to two questions above and the safety of treatments, toxicities of agents involving chloroquine, hydroxychloroquine, remdesivir, favipiravir, lopiravir/ritonavir, sarilumab, tocilizumab, siltuximab, corticosteroids and bromhexine which are the most frequently used in both Turkey and all over the world will be summarized. Conclusion: Among these drugs favipiravir seems the most promising drug due to more tolerable adverse effects. More clinical trials with large sample sizes are needed to find the most effective and safe drug for COVID-19 treatment.

Updated picture of SARS-CoV-2 variants and mutations

Diagnosis ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Giuseppe Lippi ◽  
Camilla Mattiuzzi ◽  
Brandon M. Henry
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Preventive Measures ◽  
Definitive Treatment ◽  
Social Distancing ◽  
Viral Spread ◽  
Limited Efficacy ◽  
Highly Virulent ◽  
New Mutations

Abstract The worldwide burden of coronavirus disease 2019 (COVID-19) is still unremittingly prosecuting, with nearly 300 million infections and over 5.3 million deaths recorded so far since the origin of the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic at the end of the year 2019. The fight against this new highly virulent beta coronavirus appears one of the most strenuous and long challenges that humanity has ever faced, since a definitive treatment has not been identified so far. The adoption of potentially useful physical preventive measures such as lockdowns, social distancing and face masking seems only partially effective for mitigating viral spread, though efficacy and continuation of such measures on the long term is questionable, due to many social and economic reasons. Many COVID-19 vaccines have been developed and are now widely used, though their effectiveness is challenged by several aspects such as low uptake and limited efficacy in some specific populations, as well as by continuous emergence of new mutations in the SARS-CoV-2 genome, accompanying the origin and spread of new variants, which in turn may contribute to further decrease the effectiveness of current vaccines and treatments. This article is hence aimed to provide an updated picture of SARS-CoV-2 variants and mutations that have emerged from November 2019 to present time (i.e., early December 2021).

scholarly journals COVID-19 Time-varying Reproduction Numbers Worldwide: An Empirical Analysis of Mandatory and Voluntary Social Distancing

2021 ◽  
Vol 2021 (407) ◽  
Author(s):  
Alexander Chudik ◽  
◽  
M. Hashem Pesaran ◽  
Alessandro Rebucci ◽  
◽  
...  
Keyword(s):  
Empirical Analysis ◽  
Time Varying ◽  
Social Distancing ◽  
Reproduction Numbers

scholarly journals Delaying the COVID-19 epidemic in Australia: Evaluating the effectiveness of international travel bans

2020 ◽  
Author(s):  
Adeshina I. Adekunle ◽  
Michael Meehan ◽  
Dianna Rojas ◽  
James Trauer ◽  
Emma McBryde
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
International Travel ◽  
Control Measures ◽  
Social Distancing ◽  
Novel Virus

AbstractFollowing the outbreak of novel Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) or COVID-19 in Wuhan, China late 2019, different countries have put in place interventions such as travel ban, proper hygiene, and social distancing to slow the spread of this novel virus. We evaluated the effects of travel bans in the Australia context and projected the epidemic until May 2020. Our modelling results closely align with observed cases in Australia indicating the need for maintaining or improving on the control measures to slow down the virus.

EDUKASI MASYARAKAT MELALUI AKTIVITAS RELAWAN NON MEDIS DALAM MEMUTUS RANTAI PENYEBARAN COVID-19 DI LINGKUNGAN CAKRANEGARA UTARA

2020 ◽  
Vol 2 (1) ◽  
pp. 150
Author(s):  
Maruni Wiwin Diarti ◽  
Yunan Jiwintarum ◽  
Awan Dramawan
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Social Distancing

Coronavirus Disease 2019 (Covid-19) adalah penyakit menular yang disebabkan oleh Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). WHO sudah menetapkan Covid-19 sebagai pandemi. Virus Covid-19 umumnya ditransmisikan melalui kontak fisik erat dan percikan (droplet) dari saluran pernapasan, sedangkan transmisi melalui udara (airborne) dapat terjadi saat melakukan prosedur medis yang menghasilkan aerosol.  Cakranegara Utara merupakan salah satu kelurahan di Kota Mataram yang sampai dengan bulan Agustus 2020 masih ditetapkan sebagai Zona merah.  Peran masyarakat diakui cukup penting untuk menekan kasus Covid-19 yang terus bertambah.  Relawan non medis merupakan kelompok mahasiswa yang peduli terhadap Covid-19.  Pendekatan edukasi masyarakat melalui aktivitas relawan non medis dalam kegiatan pengabdian masyarakat ini diharapkan dapat mencegah penyebaran Covid 19 di lingkungan Cakranegara Utara. Metode yang digunakan dalam Edukasi Masyarakat melalui aktivitas relawan non medis dalam memutus rantai penularan Covid-19 melalui ceramah, metode diskusi dan metode demonstrasi. Untuk mengetahui keberhasilan edukasi pada masyarakat melalui aktivitas relawan non medis ini dilakukan pretest dan posttest pada masyarakat. Hasil menunjukkan terjadi peningkatan pengetahuan masyarakat mengenai cara cuci tangan yang benar (WHO), Covid-19 dan pencegahannya dan Edukasi masyarakat melalui aktivitas relawan non medis dapat meningkatkan pengetahuan masyarakat tentang tentang cara mencuci tangan dengan benar (WHO), Covid-19 dan cara pencegahannya, social distancing dan manfaat pengunaan masker untuk memutus rantai penularan Covid-19.

scholarly journals Epidemiological trend of COVID-19 in Nepal and the importance of social distancing to contain the virus

2020 ◽  
Vol 1 (1) ◽  
pp. 15-25
Author(s):  
Amod K. Pokhrel ◽  
Yadav P. Joshi ◽  
Sopnil Bhattarai
Keyword(s):  
Mitigation Measures ◽  
Contact Tracing ◽  
Limited Information ◽  
Social Distancing ◽  
Mobility Data ◽  
Epidemiological Trend ◽  
Reproduction Numbers ◽  
The Government ◽  
Testing Case ◽  
The Impact

There is limited information on the epidemiology and the effects of mitigation measures on the spread of COVID-19 in Nepal. Using publicly available databases, we analyzed the epidemiological trend, the people's movement trends at different intervals across different categories of places and evaluated implications of social mobility on COVID-19. We also estimated the epidemic peak. As of June 9, 2020, Provinces 2 and 5 have most of the cases. People between 15 and 54 years are vulnerable to becoming infected, and more males than females are affected. The cases are growing exponentially. The growth rate of 0.13 and >1 reproduction numbers (R0) over time (median: 1.48; minimum: 0.58, and maximum: 3.71) confirms this trend. The case doubling time is five days. Google's community mobility data suggest that people strictly followed social distancing measures for one month after the lockdown. By around the 4th week of April, the individual's movement started rising, and social contacts increased. The number of cases peaked on May 12, with 83 confirmed cases in one day. The Susceptible-Exposed-Infectious-Removed (SEIR) model suggests that the epidemic will peak approximately on day 41 (July 21, 2020), and start to plateau after day 80. To contain the spread of the virus, people should maintain social distancing. The Government needs to continue active surveillance, more PCR-based testing, case detection, contact tracing, isolation, and quarantine. The Government should also provide financial support and safety-nets to the citizen to limit the impact of COVID-19.

scholarly journals Social Distancing to Mitigate COVID-19 Risks Is Associated With COVID-19 Discriminatory Attitudes Among People Living with HIV

2020 ◽  
Vol 54 (10) ◽  
pp. 728-737
Author(s):  
Marcie Berman ◽  
Lisa A Eaton ◽  
Ryan J Watson ◽  
J L Andrepont ◽  
Seth Kalichman
Keyword(s):  
Social Sciences ◽  
Public Health ◽  
Severe Acute Respiratory Syndrome ◽  
Ongoing Study ◽  
People Living With Hiv ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Immune Systems ◽  
Social Distancing ◽  
Living With Hiv

Abstract Background Severe acute respiratory syndrome coronavirus-2, the virus that causes COVID-19, is an emerging pandemic with heightened concerns for people with compromised immune systems, including people living with HIV. Purpose In the absence of a vaccine, public health messaging to mitigate risks for COVID-19 primarily focuses on social distancing. Because people living with HIV commonly experience mistreatment associated with HIV, their response to social distancing may be complicated by psychosocial attitudes associated with COVID-19. Methods To evaluate these relationships, we conducted a rapid-response, cross-sectional survey with people living with HIV (N = 149) to assess social distancing practices, COVID-19 discriminatory attitudes, COVID-19 xenophobic attitudes, HIV microaggressions, and concern over contracting COVID-19. Data were collected from participants enrolled in a larger ongoing study between March 30, 2020 and April 17, 2020. Results Results indicated that choosing to socially distance to reduce COVID-19 exposure was associated with COVID-19 discriminatory attitudes, concerns of contracting COVID-19, and identifying as transgender. Likewise, social distancing imposed by others (e.g., cancelations and restrictions) was associated with concerns of contracting COVID-19. Conclusions Findings demonstrate that social distancing measures are related to concerns of contracting the virus and discriminatory attitudes toward those who are presumed to be living with COVID-19. These potentially negative psychosocial attitudes toward people perceived to have COVID-19 echo the discriminatory actions and attitudes that we continue to observe in HIV social sciences research.

scholarly journals The Importance of Advancing Severe Acute Respiratory Syndrome Coronavirus 2 Vaccines in Children

2020 ◽  
Author(s):  
Carol M Kao ◽  
Walter A Orenstein ◽  
Evan J Anderson
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Herd Immunity ◽  
Target Population ◽  
Indirect Benefit ◽  
Direct Benefit ◽  
Potential Barriers ◽  
Community Protection ◽  
Role Based ◽  
Childhood Vaccines

Abstract While the role of children in the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains to be defined, children likely play an important role based on our knowledge of other respiratory viruses. Children are more likely to be asymptomatic or have milder symptoms and less likely to present for healthcare and be tested for SARS-CoV-2. Thus, our current estimates are likely under-representative of the true burden of SARS-CoV-2 in children. Given the potential direct benefit of a SARS-CoV-2 vaccine in children and the substantial indirect benefit through community protection, or “herd immunity,” we argue that planning and implementation of SARS-CoV-2 vaccines should include children. Furthermore, community protection occurred after widespread implementation of prior childhood vaccines against Streptococcus pneumoniae, rubella, and rotavirus. We detail considerations for vaccine clinical trials, potential barriers to the implementation of widespread vaccination and argue why children would be an ideal target population for vaccination.

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