Vaccine epidemiology, evaluation, and constraints of vaccine effectiveness -A review

Abstract

Vaccines are all biological substances produced from living things, administered to trigger the host's body defense system to develop immunity against a specific pathogen from which they are produced. They are produced either from the whole organism or parts of it. There are several types of vaccines like live virulent, live attenuated, inactivated (killed), subunit, toxoid, sero-vaccine, and autogenous vaccine. Vaccines work by stimulating either humoral or cell-mediated immunity or both to differentiate. Even though vaccination is the powerful and cost-effective weapon of disease prevention and control of infectious and non infectious diseases, there are factors those, hinder its effectiveness (constraints of vaccine effectiveness). These factors are technical constraints, pathogen-related constraints, vaccine-related factors, host-related and environmental and management-related constraints. While planning a vaccination regimen, it is important to test the potency of the vaccine, whether it much with circulating serotype, availability of cold chain, skilled manpower, the status of the target group and weather condition. Vaccine epidemiology, the study of vaccine interactions and impacts on the epidemiology of vaccine-preventable diseases also has an impact on vaccine effectiveness. it includes basic reproductive number, the force of infection, herd immunity, and epidemiologic shift. Some review papers mostly deal with constraints of specific vaccines and species of animals and with a specific constraint of the vaccine. However, the papers which review all common constraints of vaccine are limited. Therefore, this review paper is to address the most common constraints on the effectiveness of vaccines in all animal species and to highlight on evaluation of vaccine effectiveness and epidemiology.