Post mass-immunization measles outbreak in Taoyuan county, Taiwan: Dynamics of transmission, vaccine effectiveness, and herd immunity

Abstract Background The COVID-19 pandemic has disrupted routine measles immunisation and supplementary immunisation activities (SIAs) in most countries including Kenya. We assessed the risk of measles outbreaks during the pandemic in Kenya as a case study for the African Region. Methods Combining measles serological data, local contact patterns, and vaccination coverage into a cohort model, we predicted the age-adjusted population immunity in Kenya and estimated the probability of outbreaks when contact-reducing COVID-19 interventions are lifted. We considered various scenarios for reduced measles vaccination coverage from April 2020. Results In February 2020, when a scheduled SIA was postponed, population immunity was close to the herd immunity threshold and the probability of a large outbreak was 34% (8–54). As the COVID-19 contact restrictions are nearly fully eased, from December 2020, the probability of a large measles outbreak will increase to 38% (19–54), 46% (30–59), and 54% (43–64) assuming a 15%, 50%, and 100% reduction in measles vaccination coverage. By December 2021, this risk increases further to 43% (25–56), 54% (43–63), and 67% (59–72) for the same coverage scenarios respectively. However, the increased risk of a measles outbreak following the lifting of all restrictions can be overcome by conducting a SIA with ≥ 95% coverage in under-fives. Conclusion While contact restrictions sufficient for SAR-CoV-2 control temporarily reduce measles transmissibility and the risk of an outbreak from a measles immunity gap, this risk rises rapidly once these restrictions are lifted. Implementing delayed SIAs will be critical for prevention of measles outbreaks given the roll-back of contact restrictions in Kenya.

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The Long Road Toward COVID-19 Herd Immunity: Vaccine Platform Technologies and Mass Immunization Strategies

Frontiers in Immunology ◽

10.3389/fimmu.2020.01817 ◽

2020 ◽

Vol 11 ◽

Cited By ~ 7

Author(s):

Lea Skak Filtenborg Frederiksen ◽

Yibang Zhang ◽

Camilla Foged ◽

Aneesh Thakur

Keyword(s):

Herd Immunity ◽

Vaccine Platform ◽

Immunization Strategies ◽

Mass Immunization

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Measles Outbreak Associated With Low Vaccine Effectiveness Among Adults in Pohnpei State, Federated States of Micronesia, 2014

Open Forum Infectious Diseases ◽

10.1093/ofid/ofw064 ◽

2016 ◽

Vol 3 (2) ◽

Cited By ~ 15

Author(s):

Craig M. Hales ◽

Eliaser Johnson ◽

Louisa Helgenberger ◽

Mark J. Papania ◽

Maribeth Larzelere ◽

...

Keyword(s):

Confidence Interval ◽

Vaccination Campaign ◽

Vaccine Effectiveness ◽

Mass Vaccination ◽

Cold Chain ◽

Primary Case ◽

Federated States Of Micronesia ◽

Measles Outbreak ◽

Mass Vaccination Campaign ◽

Vaccination Campaigns

Abstract Background. A measles outbreak in Pohnpei State, Federated States of Micronesia in 2014 affected many persons who had received ≥1 dose of measles-containing vaccine (MCV). A mass vaccination campaign targeted persons aged 6 months to 49 years, regardless of prior vaccination. Methods. We evaluated vaccine effectiveness (VE) of MCV by comparing secondary attack rates among vaccinated and unvaccinated contacts after household exposure to measles. Results. Among 318 contacts, VE for precampaign MCV was 23.1% (95% confidence interval [CI], −425 to 87.3) for 1 dose, 63.4% (95% CI, −103 to 90.6) for 2 doses, and 95.9% (95% CI, 45.0 to 100) for 3 doses. Vaccine effectiveness was 78.7% (95% CI, 10.1 to 97.7) for campaign doses received ≥5 days before rash onset in the primary case and 50.4% (95% CI, −52.1 to 87.9) for doses received 4 days before to 3 days after rash onset in the primary case. Vaccine effectiveness for most recent doses received before 2010 ranged from 51% to 57%, but it increased to 84% for second doses received in 2010 or later. Conclusions. Low VE was a major source of measles susceptibility in this outbreak; potential reasons include historical cold chain inadequacies or waning of immunity. Vaccine effectiveness of campaign doses supports rapid implementation of vaccination campaigns in outbreak settings.

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Efficacy of the CoronaVac® Vaccine in a Region of the Colombian Amazon, Was Herd Immunity Achieved?

10.21203/rs.3.rs-593936/v1 ◽

2021 ◽

Author(s):

Salim Mattar ◽

Héctor Serrano-Coll ◽

Hollman Miller ◽

Camilo Guzmán ◽

Ricardo Rivero ◽

...

Keyword(s):

Developing Countries ◽

Observational Study ◽

Urban Population ◽

Herd Immunity ◽

Severe Infection ◽

Mass Vaccination ◽

Mild Disease ◽

Immunization Strategies ◽

Mass Immunization ◽

Colombian Amazon

Abstract Introduction. Currently, more than 1.8 billion doses of SARS-CoV-2 vaccines have been applied worldwide. However, some developing countries are still a long way from achieving herd immunity through vaccination. In some territories, such as the Colombian Amazon, mass immunization strategies have been implemented with the CoronaVac® vaccine. Due to its proximity to Brazil, where one of the variants of interest of SARS-CoV-2 circulates. Objective. To determine the efficacy of the CoronaVac® vaccine in a population of the Colombian Amazon. Methods. Between February 24, 2021, and May 19, 2021, a descriptive observational study was carried out in which a population of individuals over 18 years of age immunized with two doses of the CoronaVac® vaccine was evaluated. The study site was in the municipality of Mitú, Vaupés, in southeastern Colombia, a region located in the Amazon bordering Brazil. Results. 87% of the urban population of the Mitú municipality were vaccinated with CoronaVac®. To date, 2.1% of vaccinated individuals have become ill, and only 0.1% of these require hospitalization. No deaths attributable to COVID-19 have been reported among vaccinated individuals, and the vaccine has shown 97% efficacy against mild disease and 100% against severe infection. Conclusions. The herd immunity achieved through mass vaccination in this population has made it possible to reduce the rate of complicated cases and mortality from COVID-19 in this region of the Colombian Amazon.

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Vaccination Against COVID-19: Emerging Issues and Future Prospects

Annals of the Russian academy of medical sciences ◽

10.15690/vramn1672 ◽

2021 ◽

Vol 76 (6) ◽

pp. 652-660

Author(s):

Gennadiy G. Onischenko ◽

Tatiana E. Sizikova ◽

Vitaliy N. Lebedev ◽

Sergey V. Borisevich

Keyword(s):

Effective Means ◽

Herd Immunity ◽

High Rate ◽

Vaccination Rates ◽

Actual Duration ◽

Entire Duration ◽

Mass Immunization ◽

Emerging Issues ◽

First Time

The most effective means of combating the COVID-19 pandemic s the formation of herd immunity, with the formation of an immune population to infection. Vaccination rates are continuously increasing. In early February 2021, WHO announced that the number of people vaccinated against the disease for the first time exceeded the number of infected. In early June 2021 the vaccinated number exceeded 2 billion which is more than 12 times the total number infected for the entire duration of the pandemic. The high rate of vaccination leads to the formulation of a number of questions concerning the effectiveness of vaccines currently used for mass immunization the level of herd immunity, necessary to stop the spread of the disease, the actual duration of the vaccination carried out, long-term prospects of the platforms, used in the creation of vaccines. The purpose of this paper is to substantiate reasoned answers to the questions posed.

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Effectiveness and safety of SARS-CoV-2 vaccine in real-world studies: a systematic review and meta-analysis

Infectious Diseases of Poverty ◽

10.1186/s40249-021-00915-3 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Qiao Liu ◽

Chenyuan Qin ◽

Min Liu ◽

Jue Liu

Keyword(s):

Adverse Events ◽

Incidence Rate ◽

Real World ◽

Fixed Effects ◽

Meta Analysis ◽

Immune Surveillance ◽

Herd Immunity ◽

Vaccine Safety ◽

Vaccine Effectiveness ◽

Alpha Variant

Abstract Background To date, coronavirus disease 2019 (COVID-19) becomes increasingly fierce due to the emergence of variants. Rapid herd immunity through vaccination is needed to block the mutation and prevent the emergence of variants that can completely escape the immune surveillance. We aimed to systematically evaluate the effectiveness and safety of COVID-19 vaccines in the real world and to establish a reliable evidence-based basis for the actual protective effect of the COVID-19 vaccines, especially in the ensuing waves of infections dominated by variants. Methods We searched PubMed, Embase and Web of Science from inception to July 22, 2021. Observational studies that examined the effectiveness and safety of SARS-CoV-2 vaccines among people vaccinated were included. Random-effects or fixed-effects models were used to estimate the pooled vaccine effectiveness (VE) and incidence rate of adverse events after vaccination, and their 95% confidence intervals (CI). Results A total of 58 studies (32 studies for vaccine effectiveness and 26 studies for vaccine safety) were included. A single dose of vaccines was 41% (95% CI: 28–54%) effective at preventing SARS-CoV-2 infections, 52% (31–73%) for symptomatic COVID-19, 66% (50–81%) for hospitalization, 45% (42–49%) for Intensive Care Unit (ICU) admissions, and 53% (15–91%) for COVID-19-related death; and two doses were 85% (81–89%) effective at preventing SARS-CoV-2 infections, 97% (97–98%) for symptomatic COVID-19, 93% (89–96%) for hospitalization, 96% (93–98%) for ICU admissions, and 95% (92–98%) effective for COVID-19-related death, respectively. The pooled VE was 85% (80–91%) for the prevention of Alpha variant of SARS-CoV-2 infections, 75% (71–79%) for the Beta variant, 54% (35–74%) for the Gamma variant, and 74% (62–85%) for the Delta variant. The overall pooled incidence rate was 1.5% (1.4–1.6%) for adverse events, 0.4 (0.2–0.5) per 10 000 for severe adverse events, and 0.1 (0.1–0.2) per 10 000 for death after vaccination. Conclusions SARS-CoV-2 vaccines have reassuring safety and could effectively reduce the death, severe cases, symptomatic cases, and infections resulting from SARS-CoV-2 across the world. In the context of global pandemic and the continuous emergence of SARS-CoV-2 variants, accelerating vaccination and improving vaccination coverage is still the most important and urgent matter, and it is also the final means to end the pandemic. Graphical Abstract

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Measles Outbreak Amplified in a Pediatric Ward: Lyantonde District, Uganda, August 2017

10.21203/rs.2.12738/v3 ◽

2020 ◽

Author(s):

Claire Biribawa ◽

Joselyn Annet Atuhairwe ◽

Lilian Bulage ◽

Denis Othuba Okethwangu ◽

Benon Kwesiga ◽

...

Keyword(s):

Vaccination Coverage ◽

Case Control Study ◽

Conditional Logistic Regression ◽

Case Control ◽

Vaccine Effectiveness ◽

Pediatric Ward ◽

Probable Case ◽

Measles Outbreak ◽

Isolation Ward ◽

Control Study

Abstract Background: Measles is a highly infectious viral disease. In August 2017, Lyantonde District, Uganda reported a measles outbreak to Uganda Ministry of Health. We investigated the outbreak to assess the scope, factors facilitating transmission, and recommend control measures. Methods: We defined a probable case as sudden onset of fever and generalized rash in a resident of Lyantonde, Lwengo, or Rakai Districts from 1 June-30 September 2017, plus ≥1 of the following: coryza, conjunctivitis, or cough. A confirmed case was a probable case with serum positivity of measles-specific IgM. We conducted a neighborhood- and age-matched case-control study to identified exposure factors, and used conditional logistic regression to analyze the data. We estimated vaccine effectiveness and vaccination coverage. Findings: We identified 81 cases (75 probable, 6 confirmed); 4 patients (4.9%) died. In the case-control study, 47% of case-patients and 2.3% of controls were hospitalized at Lyantonde Hospital pediatric department for non-measles conditions 7-21 days before case-patient’s onset (OR adj =34, 95%CI: 5.1-225). Estimated vaccine effectiveness was 95% (95%CI: 75-99%) and vaccination coverage was 76% (95%CI: 68-82%). During the outbreak, an “isolation” ward was established inside the general pediatric ward where there was mixing of both measles and non-measles patients. Conclusions This outbreak was amplified by nosocomial transmission and facilitated by low vaccination coverage. We recommended moving the isolation ward outside of the building, supplemental vaccination, and vaccinating pediatric patients during measles outbreaks.

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Effectiveness of the CoronaVac® vaccine in a region of the Colombian Amazon, was herd immunity achieved?

Tropical Diseases Travel Medicine and Vaccines ◽

10.1186/s40794-021-00159-x ◽

2022 ◽

Vol 8 (1) ◽

Author(s):

Héctor Serrano-Coll ◽

Hollman Miller ◽

Camilo Guzmán ◽

Ricardo Rivero ◽

Bertha Gastelbondo ◽

...

Keyword(s):

Urban Population ◽

Indigenous Population ◽

Herd Immunity ◽

Severe Infection ◽

Mass Vaccination ◽

List Type ◽

Mild Disease ◽

Immunization Strategies ◽

Mass Immunization ◽

Colombian Amazon

Abstract Introduction Currently, more than 4.5 billion doses of SARS-CoV-2 vaccines have been applied worldwide. However, some developing countries are still a long way from achieving herd immunity through vaccination. In some territories, such as the Colombian Amazon, mass immunization strategies have been implemented with the CoronaVac® vaccine. Due to its proximity to Brazil, where one of the variants of interest of SARS-CoV-2 circulates. Objective To determine the effectiveness of the CoronaVac® vaccine in a population of the Colombian Amazon. Methods Between February 24, 2021, and August 10, 2021, a descriptive observational study was carried out in which a population of individuals over 18 years of age immunized with two doses of the CoronaVac® vaccine was evaluated. The study site was in the municipality of Mitú, Vaupés, in southeastern Colombia, a region located in the Amazon bordering Brazil. Results. 99% of the urban population of the Mitú municipality were vaccinated with CoronaVac®. To date, 5.7% of vaccinated individuals have become ill, and only 0.1% of these require hospitalization. One death was attributable to COVID-19 has been reported among vaccinated individuals, and the vaccine has shown 94.3% effectiveness against mild disease and 99.9% against severe infection. Conclusions The herd immunity achieved through mass vaccination in this population has made it possible to reduce the rate of complicated cases and mortality from COVID-19 in this region of the Colombian Amazon. Highlights CoronaVac® has shown 94.3% effectiveness against mild disease and 99.9% against severe infection in this indigenous population. CoronaVac® reduces the mortality rate from 2.2% in 2020 to 0.22% in 2021. The herd immunity was achieved through mass vaccination in this region of the Colombian Amazon.

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Prevention of COVID-19 by mRNA-based vaccines within the general population of California

Clinical Infectious Diseases ◽

10.1093/cid/ciab640 ◽

2021 ◽

Author(s):

Kristin L Andrejko ◽

Jake Pry ◽

Jennifer F Myers ◽

Nicholas P Jewell ◽

John Openshaw ◽

...

Keyword(s):

General Population ◽

Herd Immunity ◽

Asymptomatic Infection ◽

Geographic Region ◽

Vaccine Effectiveness ◽

Vaccine Hesitancy ◽

Molecular Diagnostic ◽

California Department ◽

Molecular Diagnostic Test ◽

To Receive

Abstract Background Estimates of COVID-19 vaccine effectiveness under real-world conditions, and understanding of barriers to uptake, are necessary to inform vaccine rollout. Methods We enrolled cases (testing positive) and controls (testing negative) from among the population whose SARS-CoV-2 molecular diagnostic test results from 24 February-29 April 2021 were reported to the California Department of Public Health. Participants were matched on age, sex, and geographic region. We assessed participants’ self-reported history of mRNA-based COVID-19 vaccine receipt (BNT162b2 and mRNA-1273). Participants were considered fully vaccinated two weeks after second dose receipt. Among unvaccinated participants, we assessed willingness to receive vaccination. We measured vaccine effectiveness (VE) via the matched odds ratio of prior vaccination, comparing cases with controls. Results We enrolled 1023 eligible participants aged ≥18 years. Among 525 cases, 71 (13.5%) received BNT162b2 or mRNA-1273; 20 (3.8%) were fully vaccinated with either product. Among 498 controls, 185 (37.1%) received BNT162b2 or mRNA-1273; 86 (16.3%) were fully vaccinated with either product. Two weeks after second dose receipt, VE was 87.0% (95% confidence interval: 68.6-94.6%) and 86.2% (68.4-93.9%) for BNT162b2 and mRNA-1273, respectively. Fully vaccinated participants receiving either product experienced 91.3% (79.3-96.3%) and 68.3% (27.9-85.7%) VE against symptomatic and asymptomatic infection, respectively. Among unvaccinated participants, 42.4% (159/375) residing in rural regions and 23.8% (67/281) residing in urban regions reported hesitancy to receive COVID-19 vaccination. Conclusions Authorized mRNA-based vaccines are effective at reducing documented SARS-CoV-2 infections within the general population of California. Vaccine hesitancy presents a barrier to reaching coverage levels needed for herd immunity.

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