Establish Herd Immunity Research Articles

Monitoring and evaluation of provincial classical swine fever immunization implementation with an E2 subunit vaccine in Jeju Island, South Korea.

Accidental vaccination with a live attenuated low-virulence strain of Miyagi (LOM) vaccine led to the reemergence of classical swine fever virus (CSFV) in Jeju province, South Korea in 2014. To control the continual outbreaks of LOM-derived CSFV, the provincial government launched a provincial mass vaccination project using a CSF-E2 subunit vaccine. We conducted this study to assess the herd immunity level and outcomes of E2 vaccine-based immunization in breeding and growing herds on Jeju Island during 2020-2021. A large-scale vaccination trial using the Bayovac CSF-E2 vaccine investigated its efficacy in breeding and growing herds under farm application conditions (10 CSFV-affected and three CSFV-naïve swine farms). The level of herd immunity in each farm was classified into three (S1-S3) and six (G1-G6) profiles in breeding and growing herds, respectively. Immunity monitoring revealed a remarkable improvement in the herd immunity status in all farms. The majority (10/13) of farms, including CSFV-free farms, showed the S1G1 immunity profile in 2021, indicating the appropriate implementation of the advised vaccination regime. Moreover, there were significant decreases in Erns seropositivity from 100% to 50% and 25.9% to 4.3% at farm and pig levels, respectively. In particular, all farms were confirmed as CSFV free in the growing-finishing herds. Our large-scale trial demonstrated the effectiveness of the E2 subunit vaccine in establishing herd immunity stabilization and eliminating CSFV circulation in the affected farms and highlighted the need for a provincial vaccination policy to regain the CSF-free status on Jeju Island.

Effectiveness of Adapted COVID-19 Vaccines and Ability to Establish Herd Immunity against Omicron BA.1 and BA4-5 Variants of SARS-CoV-2.

The emergence of novel SARS-CoV-2 variants has raised concerns about the ability of COVID-19 vaccination programs to establish adequate herd immunity levels in the population. This study assessed the effectiveness of adapted vaccines in preventing SARS-CoV-2 infection and the ability of the adapted vaccines to establish herd immunity against emerging Omicron variants. A systematic literature review was conducted to estimate the absolute vaccine effectiveness (aVE) in preventing SARS-CoV-2 infection using adapted vaccines targeting Omicron variants. The ability of the adapted vaccines to establish herd immunity was assessed by taking into account the following factors: aVE, Ro values of SARS-CoV-2 and the use of non-pharmacological interventions (NPIs). This study found meta-analysis-based aVEs in preventing severe disease and SARS-CoV-2 infection of 56-60% and 36-39%, respectively. Adapted vaccines could not establish herd immunity against the Omicron BA.1 and BA.4-5 variants without using non-pharmacological interventions (NPIs). The adapted vaccines could establish herd immunity only by achieving >80% vaccination coverage, using NPIs with greater effectiveness and when 20-30% of individuals were already protected against SARS-CoV-2 in the population. New adapted COVID-19 vaccines with greater effectiveness in preventing SARS-CoV-2 infection must be developed to increase herd immunity levels against emerging SARS-CoV-2 variants in the population.

VACCINE ACCEPTANCE AMONG LATE RECIPIENTS OF COVID-19 VACCINATION IN KEDAH, MALAYSIA: AN EXPLORATORY STUDY

COVID-19 vaccine availability has helped many countries around the world in alleviating the health and economic crisis caused by the pandemic. However, the smoothness of its implementation was slightly affected due to several issues such as hesitancy and even total refusal, due to several specific factors. To establish herd immunity, an adequate amount of immunization is necessary, and this issue needs to be addressed appropriately to avoid failure in efforts to curb the spread of the disease. In identifying appropriate and effective strategies to deal with this, it is important to know the factors that can influence such individuals to change their minds and eventually agree to be vaccinated. This study explores the reasons behind COVID-19 vaccine acceptance among nineteen (n=19) late vaccine recipients who initially delay or refuse to be vaccinated, using an in-depth interview method and thematic analysis. Four themes and eight subthemes were identified, emphasizing the significant role of real evidence, health risk-related perceptions, peer recommendations, and higher authority enforcement in influencing the participants to finally make a U-turn. The findings of this study can be used to formulate strategies to increase vaccine acceptance rates, especially among individuals who are still reluctant.

Comparison of Achievements in the Implementation of COVID-19 Vaccination in Five Provinces to Establish Herd Immunity in Indonesia in the Perspective of the New Public Service.

This study aims to analyze the achievements of coronavirus disease-2019 (COVID-19) vaccination in five provinces in Indonesia, North Maluku, West Sulawesi, Maluku, West Papua, and Papua. Furthermore, to establish herd immunity in the new normal perspective. Vaccination is important because it is an effective way to build immunity. This method uses qualitative research with a Qualitative Data Analysis Software (QDAS) approach. The source of data was obtained from the official website of the government, the ministry of health, in the category of areas with low vaccination achievement, and data were also obtained by capturing news in credible official media to find the cause of the low vaccination rate in the community. The data analyst uses NVivo12 software to code and visualizes data in graphs, images, and word clouds. The findings of this study indicate that in five provinces in Indonesia, North Maluku (68%), West Sulawesi (76%), Maluku (66%), West Papua (62%), and Papua (41%), the achievement of vaccination implementation is still relatively low. Due to doubts in the community about the status of the vaccine, information and communication education from the government have not been optimal; the environment and geography vary, so it becomes an obstacle in carrying out vaccination.

Virus-Specific Stem Cell Memory CD8+ T Cells May Indicate a Long-Term Protection against Evolving SARS-CoV-2

Immune memory to SARS-CoV-2 is key for establishing herd immunity and limiting the spread of the virus. The duration and qualities of T-cell-mediated protection in the settings of constantly evolving pathogens remain an open question. We conducted a cross-sectional study of SARS-CoV-2-specific CD4+ and CD8+ T-cell responses at several time points over 18 months (30-750 days) post mild/moderate infection with the aim to identify suitable methods and biomarkers for evaluation of long-term T-cell memory in peripheral blood. Included were 107 samples from 95 donors infected during the periods 03/2020-07/2021 and 09/2021-03/2022, coinciding with the prevalence of B.1.1.7 (alpha) and B.1.617.2 (delta) variants in Bulgaria. SARS-CoV-2-specific IFNγ+ T cells were measured in ELISpot in parallel with flow cytometry detection of AIM+ total and stem cell-like memory (TSCM) CD4+ and CD8+ T cells after in vitro stimulation with peptide pools corresponding to the original and delta variants. We show that, unlike IFNγ+ T cells, AIM+ virus-specific CD4+ and CD8+ TSCM are more adequate markers of T cell memory, even beyond 18 months post-infection. In the settings of circulating and evolving viruses, CD8+ TSCM is remarkably stable, back-differentiated into effectors, and delivers immediate protection, regardless of the initial priming strain.

Vaccination practices, knowledge and attitudes regarding COVID-19 vaccines among Chinese university students: a cross-sectional study from a comprehensive university in Wuhan

ObjectiveIn China, a free national COVID-19 vaccination programme has been launched in spring 2021 and is ongoing across the country. This study aimed to preliminarily understand the current COVID-19 vaccination...

COVID-19 Vaccination Distribution and Uptake: Addressing Vaccine Hesitancy in Canada

The COVID-19 pandemic has prompted the urgent development and distribution of novel vaccinations to reduce the global disease burden and establish herd immunity. Vaccination is a cost-effective public health measure that is critical for disease prevention; as of March 2022, Health Canada has authorized the distribution of the Pfizer-BioNTech and Moderna mRNA COVID-19 vaccines in pediatric populations. However, vaccine hesitancy among caregivers remains a significant barrier to vaccine uptake in the pediatric population. Increased research on the intentions, motivations, and perceptions of pediatric COVID-19 vaccine efficacy and safety may facilitate the development of public health strategies to address pediatric vaccine knowledge translation, accessibility, and administration barriers. This perspective paper aims to explore the major barrier of vaccine hesitancy and potential solutions to achieve effective vaccine uptake in the Canadian pediatric population.

Hesitancy versus acceptability: An observational study for acceptance of COVID-19 vaccine among parents and guardians of children under 17 years age in South East Rajasthan

Background: Vaccination against COVID-19 is necessary to reach herd immunity and essential for mitigating the spread. To establish herd immunity, the immunity generated by natural infection or vaccination must prevent onward transmission, not just clinical disease. However, several studies have shown that achieving herd immunity through natural infection might be difficult. Aims and Objectives: The aim of the study is to enquire about parental acceptability for COVID-19 vaccination for their children, factors affecting acceptability, perceptions for pediatric COVID-19 vaccines. Materials and Methods: We conducted an online questionnaire survey in mode of Google form which was distributed through social media platforms to parents/guardians of children below 17 years of age in months of November and December 2021. The questionnaire had various sections: Socio demographic characteristics, family members and medical history, COVID-19-related history, attitudes toward COVID-19, attitudes toward COVID-19 vaccines, and acceptance of COVID-19 vaccination for their children. Results: The most of the parents (71.77%) were ready to vaccinate their child. Graduated parents were showing maximum acceptance. Variables related to maximum vaccine acceptance include English medium of education, higher income, COVID-19-positive member in family, vaccinated parents/guardians, and vigilant parents/guardians about child COVID vaccination. In case of side effects, 68.05% of responders agreed to follow the professional advice of personal doctor/vaccinator. About 35% of respondents want government to roll out vaccination in a phased manner. About 69% responders are in favor of making hospitals and schools as COVID-19 vaccination center for children. Conclusion: The study found high multifactorial acceptability for pediatric COVID-19 vaccination which should be rolled out in phased manner.

Addressing vaccine inequities among Ukrainian refugees

Addressing vaccine inequities among Ukrainian refugees

COVID-19 vaccine hesitancy and vaccine passports: a cross-sectional conjoint experiment in Japan

ObjectivesWhile the development of vaccines against the Novel Coronavirus (COVID-19) brought hope of establishing herd immunity and ending the global pandemic, vaccine hesitancy can hinder the progress towards herd immunity....

Percentages of Vaccination Coverage Required to Establish Herd Immunity against SARS-CoV-2.

The pandemic associated with SARS-CoV-2 is a worldwide public health challenge. The WHO has proposed to achieve 70% COVID-19 vaccination coverage in all countries by mid-2022. Nevertheless, the prevention strategy based on COVID-19 vaccination and other applied prevention measures has not been sufficient to prevent SARS-CoV-2 epidemic waves. This study assessed the vaccination coverage that would be required to establish herd immunity against SARS-CoV-2, taking into account virus transmissibility (Ro values from 1.1 to 10) and COVID-19 vaccination effectiveness. The study found that high percentages of vaccination coverage and high levels of vaccination effectiveness are necessary to block the transmission of Omicron and other SARS-CoV-2 variants with greater infectious capacity. COVID-19 vaccination programs could establish herd immunity against SARS-CoV-2, with Ro values ranging from 3 to 10 and levels of COVID-19 vaccination effectiveness of 70–100%. Factors reducing COVID-19 vaccination effectiveness (emergent variants, infections among vaccinated individuals, high risk individuals) and factors increasing SARS-CoV-2 transmissibility (close settings) increased the percentages of vaccination coverage that would be required to establish herd immunity. Two measures should be implemented to establish herd immunity against SARS-CoV-2: (1) achieve ≥ 90% COVID-19 vaccination coverage in all countries worldwide, and (2) increase the effectiveness of COVID-19 vaccines in preventing Omicron infection to at least 88%.

Covid-19 Vaccination: Rights or Obligations?

In responding to the pandemic due to the coronavirus, the Indonesian government requires the public to carry out vaccinations in order to prevent the spread of the coronavirus and establish herd immunity. This instruction contradicts that health is a form of human right that cannot be enforced. Therefore, this paper wants to examine whether COVID-19 vaccination in the midst of an pandemic situation is a form of human right or obligation. The research method used in this paper is a normative method, and the results of this paper indicate that the covid-19 vaccine during an pandemic period can be categorized as a form of human obligation for everyone based on the obligation to respect the human rights of others as stated in the State Constitution. The Republic of Indonesia in 1945.

An Appraisal of the Current Scenario in Vaccine Research for COVID-19

The recent coronavirus disease 2019 (COVID-19) outbreak has drawn global attention, affecting millions, disrupting economies and healthcare modalities. With its high infection rate, COVID-19 has caused a colossal health crisis worldwide. While information on the comprehensive nature of this infectious agent, SARS-CoV-2, still remains obscure, ongoing genomic studies have been successful in identifying its genomic sequence and the presenting antigen. These may serve as promising, potential therapeutic targets in the effective management of COVID-19. In an attempt to establish herd immunity, massive efforts have been directed and driven toward developing vaccines against the SARS-CoV-2 pathogen. This review, in this direction, is aimed at providing the current scenario and future perspectives in the development of vaccines against SARS-CoV-2.

Titers, Prevalence, and Duration of SARS-CoV-2 Antibodies in a Local COVID-19 Outbreak and Following Vaccination.

Information concerning the development of neutralizing antibodies and their duration will be critical to establishing herd immunity for COVID-19. We sought to evaluate SARS-CoV-2 spike protein receptor-binding domain (RBD)-specific antibodies, their duration, and capacity for SARS-CoV-2 neutralization in volunteers while the pandemic spread within our community starting in March 2020. Those participants with the highest starting titers had the longest-lasting response, up to 12 months post-diagnosis. SARS-CoV-2 neutralization capacity was correlated with anti-RBD antibody levels. The majority of our participants with confirmed COVID-19 diagnosis had very mild or asymptomatic infections. We also detected low and largely non-neutralizing anti-RBD IgG titers in a few participants with no known COVID-19 diagnosis. Finally, we found that antibody responses induced by vaccination were significantly higher than those induced by natural infection. Thus, our study suggests that vaccination is still critical even for those naturally infected or diagnosed with COVID-19.

Estimating asymptomatic, undetected and total cases for the COVID-19 outbreak in Wuhan: a mathematical modeling study

BackgroundThe COVID-19 outbreak in Wuhan started in December 2019 and was under control by the end of March 2020 with a total of 50,006 confirmed cases by the implementation of a series of nonpharmaceutical interventions (NPIs) including unprecedented lockdown of the city. This study analyzes the complete outbreak data from Wuhan, assesses the impact of these public health interventions, and estimates the asymptomatic, undetected and total cases for the COVID-19 outbreak in Wuhan.MethodsBy taking different stages of the outbreak into account, we developed a time-dependent compartmental model to describe the dynamics of disease transmission and case detection and reporting. Model coefficients were parameterized by using the reported cases and following key events and escalated control strategies. Then the model was used to calibrate the complete outbreak data by using the Monte Carlo Markov Chain (MCMC) method. Finally we used the model to estimate asymptomatic and undetected cases and approximate the overall antibody prevalence level.ResultsWe found that the transmission rate between Jan 24 and Feb 1, 2020, was twice as large as that before the lockdown on Jan 23 and 67.6% (95% CI [0.584,0.759]) of detectable infections occurred during this period. Based on the reported estimates that around 20% of infections were asymptomatic and their transmission ability was about 70% of symptomatic ones, we estimated that there were about 14,448 asymptomatic and undetected cases (95% CI [12,364,23,254]), which yields an estimate of a total of 64,454 infected cases (95% CI [62,370,73,260]), and the overall antibody prevalence level in the population of Wuhan was 0.745% (95% CI [0.693%,0.814%]) by March 31, 2020.ConclusionsWe conclude that the control of the COVID-19 outbreak in Wuhan was achieved via the enforcement of a combination of multiple NPIs: the lockdown on Jan 23, the stay-at-home order on Feb 2, the massive isolation of all symptomatic individuals via newly constructed special shelter hospitals on Feb 6, and the large scale screening process on Feb 18. Our results indicate that the population in Wuhan is far away from establishing herd immunity and provide insights for other affected countries and regions in designing control strategies and planing vaccination programs.

Titers, prevalence and duration of SARS-CoV-2 antibodies in two waves of a local COVID-19 outbreak

Abstract Information concerning the development of neutralizing antibodies and their duration will be critical to establishing herd immunity for COVID-19. We sought to evaluate SARS-CoV-2 spike protein receptor binding domain (RBD)-specific antibodies, their duration and capacity for SARS-CoV-2 neutralization in volunteers while the pandemic spread within our community starting in March 2020. Those participants with the highest starting titers had the longest lasting response, up to 9 months post-diagnosis. SARS-CoV-2 neutralization capacity was correlated with anti-RBD antibody levels. The majority of our participants with confirmed COVID-19 diagnosis had very mild or asymptomatic infections. We also detected low and largely non-neutralizing anti-RBD IgG titers in a few participants with no known COVID-19 diagnosis. Finally, we found that antibody responses induced by vaccination were significantly higher than those induced by natural infection. Thus, our study suggests that vaccination is still critical even for those naturally infected or diagnosed with COVID-19.

Risky behaviour and non-vaccination

Widespread vaccination acceptance is of critical import to society dealing with the continuing aftermath of the COVID-19 pandemic. The risky behaviours that predict whether individuals vaccinate for seasonal influenza can help policymakers fashion plans to improve vaccination rates and more reliably establish herd immunity. To this end, Canadian Community Health Survey (CCHS) data were employed to determine how an individual’s choice to engage in various risky behaviours relates with the likelihood that the same individual gets the seasonal influenza vaccine. Controls were included for demographic, geographic, and health insurance factors. In addition to controlling for these factors, regressions were further stratified based upon gender, the presence of children in the home, and age. I found that excess sun exposure, poor oral hygiene, smoking, and unhealthy diet choices correlated with reduced vaccination probability—both over the subsequent year and for that individual’s lifetime. These results have important implications for properly targeting individuals for widespread vaccinations.

Cluster of COVID-19 in Northern France: A Retrospective Closed Cohort Study

Background: The Oise department in France has been heavily affected by COVID-19 in early 2020. Methods: Between 30 March and 4 April 2020, we conducted a retrospective closed cohort study among pupils, their parents and siblings, as well as teachers and non-teaching staff of a high-school located in Oise. Participants completed a questionnaire that covered history of fever and/or respiratory symptoms since 13 January 2020 and had blood tested for the presence of anti-SARS-CoV-2 antibodies. The infection attack rate (IAR) was defined as the proportion of participants with confirmed SARS-CoV-2 infection based on antibody detection. Blood samples from two blood donor centres collected between 23 and 27 March 2020 in the Oise department were also tested for presence of anti-SARS-CoV-2 antibodies. Findings: Of the 661 participants (median age: 37 years), 171 participants had anti-SARS-CoV-2 antibodies. The overall IAR was 25.9% (95% confidence interval (CI) = 22.6-29.4), and the infection fatality rate was 0% (one-sided 97.5% CI = 0 - 2.1). Nine of the ten participants hospitalised since mid-January were in the infected group, giving a hospitalisation rate of 5.3% (95% CI = 2.4 –9.8). Anosmia and ageusia had high positive predictive values for SARS-CoV-2 infection (84.7% and 88.1%, respectively). Smokers had a lower IAR compared to non-smokers (7.2% versus 28.0%, P <0.001). The proportion of infected individuals who had no symptoms during the study period was 17.0% (95% CI = 11.2 – 23.4). The proportion of donors with anti-SARS-CoV-2 antibodies in two nearby blood banks of the Oise department was 3.0% (95% CI = 1.1 - 6.4). Interpretation: The relatively low IAR observed in an area where SARS-CoV-2 actively circulated weeks before confinement measures indicates that establishing herd immunity will take time, and that lifting these measures in France will be long and complex. Trial Registration: This study was registered with ClinicalTrials.gov (NCT04325646). Funding Statement: OS lab is funded by Institut Pasteur, ANRS, Sidaction, the Vaccine Research Institute (ANR10-LABX-77), Labex IBEID (ANR-10-LABX-62-IBEID), “TIMTAMDEN” ANR-14-CE14-0029, “CHIKV-ViroImmuno” ANR-14-CE14-0015-01 and the Gilead HIV cure program. LG is supported by the French Ministry of Higher Education, Research and Innovation.ME lab is funded by Institut Pasteur, Labex IBEID (ANR-10-LABX-62-IBEID), Reacting, EU grant Recover, ANR Oh’ticks. HM received core grants from the G5 Institut Pasteur Program, the Milieu Interieur Program (ANR-10-LABX-69-01) and INSERM. C.P. is supported by a fellowship from the Agence Nationale de Recherches sur le Sida et les Hepatites Virales (ANRS). SVDW lab is funded by Institut Pasteur, CNRS, Universite de Paris, Sante publique France, Labex IBEID (ANR-10-LABX-62-IBEID), REACTing, EU grant Recover. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: Ethical approval by the Comite de Protection des Personnes Ile de France III. Informed consent was obtained from all participants.

Can a COVID-19 vaccine live up to Americans' expectations? A conjoint analysis of how vaccine characteristics influence vaccination intentions.

ObjectiveA vaccine for the novel coronavirus (COVID-19) could prove critical in establishing herd immunity. While past work has documented the prevalence and correlates of vaccine refusal, I assess how a less explored topic -- properties of vaccines themselves (e.g., national origin, efficacy, risk of side effects) -- might influence vaccination intentions. This information can help public health officials preempt differential intentions to vaccinate, and inform health communication campaigns that encourage vaccine uptake.RationalePrevious research suggests that Americans should be more likely to intend to vaccinate if presented with a US-made vaccine that carries a low risk of minor side effects, is highly effective, is administered in just one dose, and has spent significant time in development.MethodsI administered a conjoint experiment (N = 5940 trials) in a demographically representative survey (N = 990) of US adults to assess how variation in vaccine properties influence self-reported public vaccination intentions.ResultsI find that respondents prefer vaccines that are US-made, over 90% effective, and carry a less than 1% risk of minor side effects. This is potentially problematic, as some leading vaccine candidates are produced outside the US, and/or may be more likely to produce minor side effects than respondents would otherwise prefer. Worryingly, intended vaccine refusal rates exceed 30% for a vaccine meeting these optimal characteristics. Encouragingly, though, Americans show no clear preference for vaccines administered in one dose, or developed in under a year, and do not appear to draw a distinction between weakened viral vs. mRNA-based vaccines.ConclusionAmericans’ preferences for a novel coronavirus vaccine may be at odds with the vaccine that ultimately hits the market, posing both policy and health communication challenges for vaccination uptake.

Herd immunity: basic concepts, epidemiological consideration and its application during pandemic like COVID-19

Herd immunity is referred as the indirect protection from infection caused to susceptible individuals when a sufficiently large population of immune individuals exist in a population. The transmission dynamics of a pathogen needs to be well characterized. The basic reproduction number R0 and the effective reproduction number Re are the centric concept in the epidemiology of an infectious disease. The point at which the proportion of susceptible individuals falls below the threshold needed for transmission is known as the herd immunity threshold, and is calculated by 1 – 1/R0. The vaccination programmes and herd immunity complement each other. Through vaccination, a randomly mixed population can be considered immune, once it reaches herd immunity threshold. The proportion of immune individuals should exceed (R0 − 1)/R0, or 1 –1/R0, in order to bring decline in the infection incidence. The vaccine based eradication programmes have been successful in achieving herd immunity for various infectious diseases. As the transmission dynamics of SARS-CoV-2 is not well understood and there are no vaccines available, the objective of establishing herd immunity seems to be theoretical. The previous outbreak of SARS-CoV had shown genome instability and hence, to comment over the indirect protection was not found to be appropriate. In the current pandemic caused by a novel virus of the same family, when the availability of vaccines might take 12-18 months, exposing the population to encounter infection with the vision of achieving indirect protection can appear to be detrimental for the nations where health care infrastructure is already not robust.