Prospective Promising Signs of Herd Iimmunity in COVID-19 Transmission Suppression via Vaccination (original) (raw)
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COVID-19: individual and herd immunity
Comptes Rendus. Biologies
Immunity to the SARS-CoV-2 virus ensures protection against reinfection by this virus thanks to the combined action of neutralizing antibodies and T lymphocytes specific to viral proteins, in particular the Spike protein. It must be distinguished from the immune response that ensures healing of the infection following contamination that involves innate immunity, particularly type 1 interferons, and which is followed by adaptive cellular and humoral immunity. The importance of the effect of interferons is highlighted by the occurrence of severe forms of the disease in genetically deficient subjects or in patients with antibodies neutralizing type 1 interferon. Herd immunity is not an individual biological property. It is a mathematical property that qualifies the fact that when the proportion of subjects with individual immunity is high enough, there is little chance that an epidemic can occur. The level of that proportion-the herd immunity of the population can be computed under theoretical, often unrealistic, hypotheses, and is difficult to assess in natural conditions.
Dynamics of Population Immunity Due to the Herd Effect in the COVID-19 Pandemic
Vaccines, 2020
The novel Coronavirus 2 Severe Acute Respiratory Syndrome (SARS-Cov-2) has led to the Coronavirus Disease 2019 (COVID-19) pandemic, which has surprised health authorities around the world, quickly producing a global health crisis. Different actions to cope with this situation are being developed, including confinement, different treatments to improve symptoms, and the creation of the first vaccines. In epidemiology, herd immunity is presented as an area that could also solve this new global threat. In this review, we present the basis of herd immunology, the dynamics of infection transmission that induces specific immunity, and how the application of immunoepidemiology and herd immunology could be used to control the actual COVID-19 pandemic, along with a discussion of its effectiveness, limitations, and applications.
Immunisation, asymptomatic infection, herd immunity and the new variants of COVID-19
2021
Objectives Is herd immunity to COVID-19 a realistic outcome of any immunisation programme with the two main vaccines currently licenced in the UK (Pfizer vaccine BNT162b2 and Astra Zeneca/Oxford vaccine ChAdOx1-S)? More formally, can these vaccines achieve a sufficient level of population immunity to reduce R, the reproduction number of the infection, to below one in the absence of any non-pharmaceutical interventions? Design The study uses simple mathematical models of the transmission of COVID-19 infection from primary to secondary cases parameterised using data on virus transmission and vaccine efficacy from the literature and the regulatory approval process for the vaccines. Results In the regulatory approval documents, the efficacy of the Pfizer vaccine is estimated at 0.948 (that for the Moderna vaccine is similar). Efficacy for the Oxford vaccine against primary symptomatic illness is estimated as 0.704, based on pooling of data from two dose regimes. For values of R0 similar...
COVID-19: Is herd immunity the answer?
Journal of Advances in Internal Medicine, 2020
The SARS-CoV-2 virus has been trans missed across the planet, with a current global total of a staggering 30,675,675 confirmed cases.The novelty, speed and ease of transmission of the virus has acted as the catalyst for the implication of both standard protocols as well as newly developed policies in order to combat and abate the transmission thereof. 3,4 Conventional measures: The measures introduced by the vast majority of countries are to Abstract The current global figures of COVID-19 is still rising. Many countries have enforced lockdowns to safeguard its citizens, however in most cases this has been to the dire detriment of the economy. Most leaders and governments have been holding out and looking to the development of a vaccine to be the answer to this COVID-19 pandemic, however at this point in time and for the foreseeable future a viable and widely available vaccine is not likely to be developed. In juxtaposition to the conventional methods countries such as Turkey have adopted the concept of herd immunity. It is there for poignant and of the upmost importance that an alternate stratagem is developed and exercised to best facilitate the re-ignition of the country's economy as well to best protect its citizens from the virus. Models such as herd immunity or a model based thereon are the most logical solution to attain this goal. At this time in the development of the global COVID-19 pandemic it is too early to conclude as to whether a fully-fledged lockdown is more effective and useful than the establishment of herd immunity. In order to achieve the goal of safeguarding the lives of a countries citizens as well as its economy, a mixed method of lockdown and herd immunity is advised. Individuals who are economically active and less susceptible to the virus should adopt the herd immunity model, whereas those who are elderly with concomitant comorbidities should exercise self-isolation and follow the lockdown model. The application of using both models simultaneously, will both capitalize on the advantages of either and negate the drawbacks thereof. This ultimately decreasing the loss of lives whilst still inducing a degree of herd immunity within the general populous.
2020
It is urgent to design and develop safe and efficacious vaccines and to establish herd immunity to stop further spread of the COVID-19 pandemic. Even though the global COVID-19 vaccine pipeline is currently expanding daily and many clinical trials to evaluate novel vaccine candidates and drug repurposing strategies for the prevention and treatment of SARS CoV-2 infection up-todate not effective, due to the nature of the virus. Even no one sure whether these trials will produce effective interventions, and it is unclear how long these studies will take to establish efficacy and safety. Hence alternative approach would be to allow the causal virus SARS-CoV-2 to spread to increase the population herd immunity.
Effect of Vaccination to COVID-19 Disease Progression and Herd Immunity
Computational and Mathematical Biophysics
A mathematical model of COVID-19 with a delay-term for the vaccinated compartment is developed. It has parameters accounting for vaccine-induced immunity delay, vaccine effectiveness, vaccination rate, and vaccine-induced immunity duration. The model parameters before vaccination are calibrated with the Philippines’ confirmed cases. Simulations show that vaccination has a significant effect in reducing future infections, with the vaccination rate being the dominant determining factor of the level of reduction. Moreover, depending on the vaccination rate and the vaccine-induced immunity duration, the system could reach a disease-free state but could not attain herd immunity. Simulations are also done to compare the effects of the various available vaccines. Results show that Pfizer-BioNTech has the most promising effect while Sinovac has the worst result relative to the others.
Herd Immunity: A Success or a Failure
INTERNATIONAL JOURNAL OF CHEMICAL AND ENVIRONMENTAL SCIENCES, 2020
Amidst the COVID-19 pandemic, the most debated scientific topic has been Herd Immunity. It may be defined as a situation in which a major portion of a population (about 60 - 90%) develops some form of the disease and, therefore, becomes resistant to it. However, with such large number of cases, the healthcare facilities are bound to get overloaded. Some patients with severe cases of COVID-19 will be required to get admitted into the ICU (intensive care units) – which have limited beds. This could lead to more preventable deaths. Herd immunity has both positive and negative aspects. For instance, if we fail in the halfway for example in the country Sweden, then it will result in more deaths rather than decreasing the spread of infection. According to several theoretical modelling that people have conducted across the world and also in India suggest that there could be few waves of COVID-19 and people need to be prepared for them. In this review we are trying to assess whether herd im...