scholarly journals Influence of heterogeneous age-group contact patterns on critical vaccination rates for herd immunity to SARS-CoV-2

2021 ◽  
Author(s):  
Joan Saldana ◽  
Caterina M Scoglio
Keyword(s):  
Vaccination Coverage ◽  
Herd Immunity ◽  
Age Groups ◽  
Social Contact ◽  
Vaccination Strategy ◽  
Primary Concern ◽  
Vaccination Rates ◽  
Contact Patterns ◽  
Group Contact ◽  
Age Structured

Currently, several western countries have more than half of their population fully vaccinated against COVID-19. At the same time, some of them are experiencing a fourth or even a fifth wave of cases, most of them concentrated in sectors of the populations whose vaccination coverage is lower than the average. So, the initial scenario of vaccine prioritization has given way to a new one where achieving herd immunity is the primary concern. Using an age-structured vaccination model with waning immunity, we show that, under a limited supply of vaccines, a vaccination strategy based on minimizing the basic reproduction number allows for the deployment of a number of vaccine doses lower than the one required for maximizing the vaccination coverage. Such minimization is achieved by giving greater protection to those age groups that, for a given social contact pattern, have smaller fractions of susceptible individuals at the endemic equilibrium without vaccination, that is, to those groups that are more vulnerable to infection.

scholarly journals Data-driven estimate of SARS-CoV-2 herd immunity threshold in populations with individual contact pattern variations

2021 ◽  
Author(s):  
Dan Lu ◽  
Alberto Aleta ◽  
Marco Ajelli ◽  
Romualdo Pastor-Satorras ◽  
Alessandro Vespignani ◽  
...  
Keyword(s):  
Herd Immunity ◽  
Vaccination Strategy ◽  
Mass Vaccination ◽  
Data Driven ◽  
Vaccination Programs ◽  
Contact Patterns ◽  
Social Mixing ◽  
Age Structured ◽  
Individual Contact ◽  
Induced Immunity

The development of efficacious vaccines has made it possible to envision mass vaccination programs aimed at suppressing SARS-CoV-2 transmission around the world. Here we use a data-driven age-structured multilayer representation of the population of 34 countries to estimate the disease induced immunity threshold, accounting for the contact variability across individuals. We show that the herd immunization threshold of random (un-prioritized) mass vaccination programs is generally larger than the disease induced immunity threshold. We use the model to test two additional vaccine prioritization strategies, transmission-focused and age-based, in which individuals are inoculated either according to their behavior (number of contacts) or infection fatality risk, respectively. Our results show that in the case of a sterilizing vaccine the behavioral strategy achieves herd-immunity at a coverage comparable to the disease-induced immunity threshold, but it appears to have inferior performance in averting deaths than the risk vaccination strategy. The presented results have potential use in defining the effects that the heterogeneity of social mixing and contact patterns has on herd immunity levels and the deployment of vaccine prioritization strategies.

scholarly journals Social contact patterns of infants in deciding vaccination strategy: a prospective, cross-sectional, single-centre study

2018 ◽  
Vol 146 (9) ◽  
pp. 1157-1166 ◽  
Author(s):  
M. M. Oguz ◽  
A. D. Camurdan ◽  
F. N. Aksakal ◽  
M. Akcaboy ◽  
E. Altinel Acoglu
Keyword(s):  
Respiratory Tract ◽  
Respiratory Symptoms ◽  
Whooping Cough ◽  
Social Contact ◽  
Vaccination Strategy ◽  
Median Number ◽  
Cross Sectional ◽  
Contact Patterns ◽  
Single Centre Study ◽  
Tract Infections

AbstractSocial contact between individuals is believed to be a fundamental cause in the transmission of many respiratory tract infections. Because they have not yet been fully vaccinated, infants are at high risk for contracting whooping cough, influenza and their serious complications. Therefore, determining infant social contact patterns is an important step in protecting them from respiratory tract infection. This study included 1200 healthy infants (<12 months of age). Social contact diaries were used to estimate the frequency and nature of the infants’ social contacts. This survey also gathered information regarding the infants’ respiratory symptoms and their frequency of attendance at crowded places over a period of 1 week. The diary return rate was 83.8% (N = 1006), and there was a total of 4706 contacts reported for these infants. The median daily contact number per capita was 4 (range 1–18). The median number of contacts with adolescents was 0 (range 0–7). Of the infants, 50.3% had contact with non-household individuals. The mothers had the longest contacts with their babies. Contacts with school children, frequency of attendance at crowded places and age were determined to be significant effective factors for reporting respiratory symptoms. Results suggest that school-age siblings and the mothers should be primarily vaccinated, and parents should keep their babies away from crowded places for protecting their infants.

scholarly journals Modelling the impact of extended vaccination strategies on the epidemiology of pertussis

2011 ◽  
Vol 140 (8) ◽  
pp. 1503-1514 ◽  
Author(s):  
M. H. ROZENBAUM ◽  
R. De VRIES ◽  
H. H. LE ◽  
M. J. POSTMA
Keyword(s):  
Booster Dose ◽  
Deterministic Model ◽  
Natural Infection ◽  
Age Groups ◽  
Vaccination Strategy ◽  
Booster Vaccination ◽  
Sensitivity Analyses ◽  
Wide Range ◽  
Age Structured ◽  
The Impact

SUMMARYThe aim of this study was to investigate the optimal pertussis booster vaccination strategy for The Netherlands. A realistic age-structured deterministic model was designed. Assuming a steady-state situation and correcting for underreporting, the model was calibrated using notification data from the period 1996–2000. Several sensitivity analyses were performed to explore the impact of different assumptions for parameters surrounded by uncertainty (e.g. duration of protection after natural infection, underreporting factors, and transmission probabilities). The optimal age of an additional booster dose is in the range of 10–15 years, and implementation of this booster dose will reduce both symptomatic and asymptomatic infections, although the incidence of symptomatic infections in older age groups will increase. The impact of the different assumptions used in the model was in general limited. We conclude that over a wide range of assumptions, an additional booster dose can reduce the incidence of pertussis in the population.

scholarly journals Contact surveys reveal heterogeneities in age-group contributions to SARS-CoV-2 dynamics in the United States

2021 ◽  
Author(s):  
Taylor Chin ◽  
Dennis M. Feehan ◽  
Caroline O. Buckee ◽  
Ayesha S. Mahmud
Keyword(s):  
United States ◽  
Age Groups ◽  
The United States ◽  
Contact Rate ◽  
Age Group ◽  
Contact Rates ◽  
Contact Patterns ◽  
Age Structured ◽  
The Impact ◽  
Over Time

SARS-CoV-2 is spread primarily through person-to-person contacts. Quantifying population contact rates is important for understanding the impact of physical distancing policies and for modeling COVID-19, but contact patterns have changed substantially over time due to shifting policies and behaviors. There are surprisingly few empirical estimates of age-structured contact rates in the United States both before and throughout the COVID-19 pandemic that capture these changes. Here, we use data from six waves of the Berkeley Interpersonal Contact Survey (BICS), which collected detailed contact data between March 22, 2020 and February 15, 2021 across six metropolitan designated market areas (DMA) in the United States. Contact rates were low across all six DMAs at the start of the pandemic. We find steady increases in the mean and median number of contacts across these localities over time, as well as a greater proportion of respondents reporting a high number of contacts. We also find that young adults between ages 18 and 34 reported more contacts on average compared to other age groups. The 65 and older age group consistently reported low levels of contact throughout the study period. To understand the impact of these changing contact patterns, we simulate COVID-19 dynamics in each DMA using an age-structured mechanistic model. We compare results from models that use BICS contact rate estimates versus commonly used alternative contact rate sources. We find that simulations parameterized with BICS estimates give insight into time-varying changes in relative incidence by age group that are not captured in the absence of these frequently updated estimates. We also find that simulation results based on BICS estimates closely match observed data on the age distribution of cases, and changes in these distributions over time. Together these findings highlight the role of different age groups in driving and sustaining SARS-CoV-2 transmission in the U.S. We also show the utility of repeated contact surveys in revealing heterogeneities in the epidemiology of COVID-19 across localities in the United States.

scholarly journals Mathematical modeling of vaccination rollout and NPIs lifting on COVID-19 transmission with VOC: a case study in Toronto, Canada

2021 ◽  
Author(s):  
Elena Aruffo ◽  
Pei Yuan ◽  
Yi Tan ◽  
Evgenia Gatov ◽  
Iain Moyles ◽  
...  
Keyword(s):  
Vaccination Coverage ◽  
Age Groups ◽  
Vaccination Strategy ◽  
The Elderly ◽  
Public Health Agencies ◽  
Initial Strategy ◽  
Working Age ◽  
Waning Immunity ◽  
Nonpharmaceutical Interventions ◽  
The Impact

ABSTRACT Background: Since December 2020, public health agencies have implemented a variety of vaccination strategies to curb the spread of SARS-CoV-2, along with pre-existing Nonpharmaceutical Interventions (NPIs). Initial strategy focused on vaccinating the elderly to prevent hospitalizations and deaths. With vaccines becoming available to the broader population, we aimed to determine the optimal strategy to enable the safe lifting of NPIs while avoiding virus resurgence. Methods: We developed a compartmental deterministic SEIR model to simulate the lifting of NPIs under different vaccination rollout scenarios. Using case and vaccination data from Toronto, Canada between December 28, 2020 and May 19, 2021, we estimated transmission throughout past stages of NPI escalation/relaxation to compare the impact of lifting NPIs on different dates on cases, hospitalizations, and deaths, given varying degrees of vaccine coverages by 20-year age groups, accounting for waning immunity. Results: We found that, once coverage among the elderly is high enough (80% with at least one dose), the main age groups to target are 20-39 and 40-59 years, whereby first-dose coverage of at least 70% by mid-June 2021 is needed to minimize the possibility of resurgence if NPIs are to be lifted in the summer. While a resurgence was observed for every scenario of NPI lifting, we also found that under an optimistic vaccination coverage (70% by mid-June, postponing reopening from August 2021 to September 2021can reduce case counts and severe outcomes by roughly 80% by December 31, 2021. Conclusions: Our results suggest that focusing the vaccination strategy on the working-age population can curb the spread of SARS-CoV-2. However, even with high vaccination coverage in adults, lifting NPIs to pre-pandemic levels is not advisable since a resurgence is expected to occur, especially with earlier reopening.

scholarly journals Assessing Age-Specific Vaccination Strategies and Post-Vaccination Reopening Policies for COVID-19 Control Using SEIR Modeling Approach

2021 ◽  
Author(s):  
Xia Wang ◽  
Hulin Wu ◽  
Sanyi Tang
Keyword(s):  
Age Structure ◽  
Age Groups ◽  
Social Contact ◽  
The Elderly ◽  
Vaccination Rate ◽  
Social Contacts ◽  
Post Vaccination ◽  
Vaccination Strategies ◽  
Contact Patterns ◽  
Effect Of Age

AbstractBackgroundAs the availability of COVID-19 vaccines, it is badly needed to develop vaccination guidelines to prioritize the vaccination delivery in order to effectively stop COVID-19 epidemic and minimize the loss.MethodsWe evaluated the effect of age-specific vaccination strategies on the number of infections and deaths using an SEIR model, considering the age structure and social contact patterns for different age groups for each of different countries.ResultsIn general, the vaccination priority should be given to those younger people who are active in social contacts to minimize the number of infections; while the vaccination priority should be given to the elderly to minimize the number of deaths. But this principle may not always apply when the interaction of age structure and age-specific social contact patterns is complicated. Partially reopening schools, workplaces or households, the vaccination priority may need to be adjusted accordingly.ConclusionsPrematurely reopening social contacts could initiate a new outbreak or even a new pandemic out of control if the vaccination rate and the detection rate are not high enough. Our result suggests that it requires at least nine months of vaccination before fully reopening social contacts in order to avoid a new pandemic.

scholarly journals Monitoring sociodemographic inequality in COVID-19 vaccination coverage in England: a national linked data study

2021 ◽  
Author(s):  
Ted Dolby ◽  
Katie Finning ◽  
Allan Baker ◽  
Leigh Dowd ◽  
Kamlesh Khunti ◽  
...  
Keyword(s):  
Language Proficiency ◽  
Vaccination Coverage ◽  
English Language ◽  
Age Groups ◽  
Population Level ◽  
Lower Percentage ◽  
Area Deprivation ◽  
Sociodemographic Characteristics ◽  
Age Group ◽  
Vaccination Rates

Background: The UK began an ambitious COVID-19 vaccination programme on 8th December 2020. This study describes variation in vaccination coverage by sociodemographic characteristics between December 2020 and August 2021. Methods: Using population-level administrative records linked to the 2011 Census, we estimated monthly first dose vaccination rates by age group and sociodemographic characteristics amongst adults aged 18 years or over in England. We also present a tool to display the results interactively. Findings: Our study population included 35,223,466 adults. A lower percentage of males than females were vaccinated in the young and middle age groups (18-59 years) but not in the older age groups. Vaccination rates were highest among individuals of White British and Indian ethnic backgrounds and lowest among Black Africans (aged ≥80 years) and Black Caribbeans (18-79 years). Differences by ethnic group emerged as soon as vaccination roll-out commenced and widened over time. Vaccination rates were also lower among individuals who identified as Muslim, lived in more deprived areas, reported having a disability, did not speak English as their main language, lived in rented housing, belonged to a lower socio-economic group, and had fewer qualifications. Interpretation: We found inequalities in COVID-19 vaccination rates by sex, ethnicity, religion, area deprivation, disability status, English language proficiency, socio-economic position, and educational attainment, but some of these differences varied by age group. Research is urgently needed to understand why these inequalities exist and how they can be addressed.

scholarly journals Combining serological and contact data to derive target immunity levels for achieving and maintaining measles elimination

BMC Medicine ◽  
2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Sebastian Funk ◽  
Jennifer K. Knapp ◽  
Emmaculate Lebo ◽  
Susan E. Reef ◽  
Alya J. Dabbagh ◽  
...  
Keyword(s):  
Measles Virus ◽  
Herd Immunity ◽  
Age Groups ◽  
Threshold Level ◽  
Specific Immunity ◽  
Measles Elimination ◽  
Contact Patterns ◽  
Wide Range ◽  
Contact Data ◽  
Serological Studies

Abstract Background Vaccination has reduced the global incidence of measles to the lowest rates in history. However, local interruption of measles virus transmission requires sustained high levels of population immunity that can be challenging to achieve and maintain. The herd immunity threshold for measles is typically stipulated at 90–95%. This figure does not easily translate into age-specific immunity levels required to interrupt transmission. Previous estimates of such levels were based on speculative contact patterns based on historical data from high-income countries. The aim of this study was to determine age-specific immunity levels that would ensure elimination of measles when taking into account empirically observed contact patterns. Methods We combined estimated immunity levels from serological data in 17 countries with studies of age-specific mixing patterns to derive contact-adjusted immunity levels. We then compared these to case data from the 10 years following the seroprevalence studies to establish a contact-adjusted immunity threshold for elimination. We lastly combined a range of hypothetical immunity profiles with contact data from a wide range of socioeconomic and demographic settings to determine whether they would be sufficient for elimination. Results We found that contact-adjusted immunity levels were able to predict whether countries would experience outbreaks in the decade following the serological studies in about 70% of countries. The corresponding threshold level of contact-adjusted immunity was found to be 93%, corresponding to an average basic reproduction number of approximately 14. Testing different scenarios of immunity with this threshold level using contact studies from around the world, we found that 95% immunity would have to be achieved by the age of five and maintained across older age groups to guarantee elimination. This reflects a greater level of immunity required in 5–9-year-olds than established previously. Conclusions The immunity levels we found necessary for measles elimination are higher than previous guidance. The importance of achieving high immunity levels in 5–9-year-olds presents both a challenge and an opportunity. While such high levels can be difficult to achieve, school entry provides an opportunity to ensure sufficient vaccination coverage. Combined with observations of contact patterns, further national and sub-national serological studies could serve to highlight key gaps in immunity that need to be filled in order to achieve national and regional measles elimination.

scholarly journals The effect of opinion clustering on disease outbreaks

2008 ◽  
Vol 5 (29) ◽  
pp. 1505-1508 ◽  
Author(s):  
Marcel Salathé ◽  
Sebastian Bonhoeffer
Keyword(s):  
Vaccination Coverage ◽  
Belief Systems ◽  
Herd Immunity ◽  
Disease Outbreaks ◽  
Disease Outbreak ◽  
High Income ◽  
Opinion Formation ◽  
Vaccine Preventable Diseases ◽  
Vaccination Rates ◽  
High Level

Many high-income countries currently experience large outbreaks of vaccine-preventable diseases such as measles despite the availability of highly effective vaccines. This phenomenon lacks an explanation in countries where vaccination rates are rising on an already high level. Here, we build on the growing evidence that belief systems, rather than access to vaccines, are the primary barrier to vaccination in high-income countries, and show how a simple opinion formation process can lead to clusters of unvaccinated individuals, leading to a dramatic increase in disease outbreak probability. In particular, the effect of clustering on outbreak probabilities is strongest when the vaccination coverage is close to the level required to provide herd immunity under the assumption of random mixing. Our results based on computer simulations suggest that the current estimates of vaccination coverage necessary to avoid outbreaks of vaccine-preventable diseases might be too low.

scholarly journals Intranasal Vaccination Strategy to Control the COVID-19 Pandemic from a Veterinary Medicine Perspective

Animals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1876
Author(s):  
Salleh Annas ◽  
Mohd Zamri-Saad
Keyword(s):  
Veterinary Medicine ◽  
Vaccination Coverage ◽  
Herd Immunity ◽  
Vaccination Strategy ◽  
Current Control ◽  
Control Measures ◽  
Vaccine Strategy ◽  
Infectious Bronchitis ◽  
Intranasal Vaccine ◽  
Potential Use

The world is currently facing an ongoing coronavirus disease 2019 (COVID-19) pandemic. The disease is a highly contagious respiratory disease which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current control measures used by many countries include social distancing, wearing face masks, frequent hand washing, self-isolation, and vaccination. The current commercially available vaccines are injectable vaccines, although a few intranasal vaccines are in trial stages. The reported side effects of COVID-19 vaccines, perceptions towards the safety of the vaccines, and frequent mutation of the virus may lead to poor herd immunity. In veterinary medicine, attaining herd immunity is one of the main considerations in disease control, and herd immunity depends on the use of efficacious vaccines and the vaccination coverage in a population. Hence, many aerosol or intranasal vaccines have been developed to control veterinary respiratory diseases such as Newcastle disease, rinderpest, infectious bronchitis, and haemorrhagic septicaemia. Different vaccine technologies could be employed to improve vaccination coverage, including the usage of an intranasal live recombinant vaccine or live mutant vaccine. This paper discusses the potential use of intranasal vaccination strategies against human COVID-19, based on a veterinary intranasal vaccine strategy.

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