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

Author(s):  
Héctor Serrano-Coll ◽  
Hollman Miller ◽  
Camilo Guzmán ◽  
Ricardo Rivero ◽  
Bertha Gastelbondo ◽  
...  

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.

2021 ◽  
Author(s):  
Salim Mattar ◽  
Héctor Serrano-Coll ◽  
Hollman Miller ◽  
Camilo Guzmán ◽  
Ricardo Rivero ◽  
...  

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.


2020 ◽  
Vol 11 ◽  
Author(s):  
Lea Skak Filtenborg Frederiksen ◽  
Yibang Zhang ◽  
Camilla Foged ◽  
Aneesh Thakur

2021 ◽  
Vol 76 (6) ◽  
pp. 652-660
Author(s):  
Gennadiy G. Onischenko ◽  
Tatiana E. Sizikova ◽  
Vitaliy N. Lebedev ◽  
Sergey V. Borisevich

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.


1987 ◽  
Vol 99 (1) ◽  
pp. 65-84 ◽  
Author(s):  
R. M. Anderson ◽  
J. A. Crombie ◽  
B. T. Grenfell

SUMMARYMathematical models and statistical analyses of epidemiological data are employed to assess the potential impact of mass vaccination on the incidences of cases of mumps infection and cases of mumps related complications. The analyses reveal that in the United Kingdom the average age at infection with the mumps virus is currently between 6–7 years and that the inter-epidemic period of the infection is approximately 3 years. The critical level of vaccine uptake to eliminate mumps virus transmission is predicted to be approximately 85% of each cohort of boys and girls by the age of 2 years. Analyses of published data show that the risk of complication arising from mumps infection is markedly age- and sex-related. Model predictions suggest that the incidence of orchitis will be increased, over the level pertaining prior to mass vaccination, by levels of vaccine uptake (by 2 years of age) that are less than 70% of each yearly cohort of boys and girls. Moderate (over 00%) to high (75%) levels of vaccine uptake, however, are predicted to reduce the overall incidence of cases of mumps related complications (especially those with CNS involvement).


Author(s):  
Wan Yang ◽  
Sasikiran Kandula ◽  
Jeffrey Shaman

PurposeTo analyze potential COVID-19 epidemic outcomes in New York City under different SARS-CoV-2 virus circulation scenarios and vaccine rollout policies from early Jan 2021 to end of June 2021.Key findingsIn anticipation of the potential arrival and dominance of the more infectious SARS-CoV-2 variant:Mass-vaccination would be critical to mitigating epidemic severity (26-52% reduction in infections, hospitalizations, and deaths, compared to no vaccination, provided the new UK variant supplants currently circulating variants).Prioritizing key risk groups for earlier vaccination would lead to greater reductions in hospitalizations and deaths than infections. Thus, in general this would be a good strategy.Current vaccination prioritization policy is suboptimal. To avert more hospitalizations and deaths, mass-vaccination of all individuals 65 years or older should be done as soon as possible. For groups listed in the same phase, 65+ year-olds should be given first priority ahead of others.Available vaccine doses should be given to the next priority groups as soon as possible without awaiting hesitant up-stream groups.While efficacy of vaccination off-protocol is unknown, provided immune response following a first vaccine dose persists, delaying the 2nd vaccine dose by ∼1 month (i.e. administer the two doses 8 weeks apart) can substantially reduce infections, hospitalizations, and deaths compared to the 3-week apart regimen. Across all scenarios tested here, delaying the 2nd vaccine dose leads to the largest reduction in severe epidemic outcomes (e.g. hospitalizations and deaths). Therefore, to protect as many people as possible, this strategy should be considered if rapid increases in infections, hospitalization or deaths and/or shortages in vaccines were to occur.


2020 ◽  
Vol 32 (2 (Supp)) ◽  
pp. 175-183 ◽  
Author(s):  
Manish Rana ◽  
Rashmi Kundapur ◽  
Amir Maroof ◽  
Vipul Chaudhari ◽  
Amiruddin Kadri ◽  
...  

COVID 19 pandemic is a global health emergency which every country is grappling with since beginning of this year.  Countries have their own strategies to cope with the cases and there have been no universal guidelines or recommendations for same. We commend the Hon. Prime Minister for taking pre-emptive timely measures to contain the pandemic at very beginning of infection in India as sustaining containment measures. Even the World Health Organisation (WHO) has acknowledged India’s efforts. According to experts for effective herd immunity about 60% of population needs to be infected, after which the infection will slow down and cases will continue to occur at low levels. For that we need good data coming from the system and government shall ensure that good data is provided for monitoring and surveillance. If all the susceptible population is exposed (without any restrictions) then we have an exponential rise in cases and our health system will be overwhelmed probably resulting in large number of deaths.  Great Britain went ahead with strategy of developing herd immunity in its population and safeguarding the elderly but after projections from Imperial College COVID 19 team, reversed their strategy to social distancing and saving lives as their health system will be overwhelmed.  COVID 19 is a mild disease for people in the younger age group while in people above the age of 60 years, the mortality is high. So staggered exposure of younger population to infection while safeguarding the elderly population at home will prevent the surge of cases and facilitate gradual development of immunity in population. Government should also focus on developing a robust health care system for screening and management of cases coupled with gradual relaxation of restriction so that health system is not overwhelmed with management of COVID 19.


2021 ◽  
Author(s):  
Alexander Sokolov ◽  
Lyubov Sokolova

AbstractA mathematical model is a reflection of knowledge on the real object studied. The paper shows how the accumulation of data (statistical data and knowledge) about the COVID-19 pandemic lead to gradual refinement of mathematical models, to the expansion of the scope of their use. The resulting model satisfactorily describes the dynamics of COVID-19 in Moscow from 19.03.2020 to 01.09.2021 and can be used for forecasting with a horizon of several months. The dynamics of the model is mainly determined by herd immunity. Monitoring the situation in Moscow has not yet (as of 01.09.2021) revealed noticeable seasonality of the disease nor an increase in infectivity (due to the Delta strain). The results of using balanced identification technology to monitor the COVID-19 pandemic are:models corresponding to the data available at different points in time (from March 2020 to August 2021);new knowledge (dependencies) acquired;forecasts for the third and fourth waves in Moscow.Discrepancies that manifested after 01.09.2021 and possible further modifications of the model are discussed


Author(s):  
Dennis L Chao

Abstract Mathematical modeling can be used to project the impact of mass vaccination on cholera transmission. Here, we discuss two examples for which indirect protection from mass vaccination needs to be considered. In the first, we show that non-vaccinees can be protected by mass vaccination campaigns. This additional benefit of indirect protection improves the cost-effectiveness of mass vaccination. In the second, we model the use of mass vaccination to eliminate cholera. In this case, a high population level of immunity, including contributions from infection and vaccination, is required to reach the “herd immunity” threshold needed to stop transmission and achieve elimination.


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