A Brief Note on Impact of Vaccines on Diseases

Corresponding Author:

Stanley Charles Department of Infectious Diseases, St George’s University Hospitals NHS Foundation Trust, London, United Kingdom E-mail: stanley_c@stguh.uk

Abstract

Introduction

One of the most significant scientific achievements of the twenty-first century has been the discovery of safe and effective vaccines against illnesses that cause significant morbidity and mortality. Vaccination, together with sanitation and safe drinking water, are public health policies that have unquestionably improved global health outcomes. Vaccines are thought to have saved 6 million lives per year from vaccine-preventable diseases. The world’s population is expected to reach about 10 billion people by 2055, thanks in part to efficient vaccinations that prevent disease and prolong average lifespan across all continents. Vaccines have had the greatest impact in reducing morbidity and mortality from severe illnesses that disproportionately affect children. Vaccines are predicted to just save 386 million life years and 96 million disability-adjusted life years (DALYs) globally each year, preventing nearly six million deaths. Vaccine efficacy, the direct protection afforded to a vaccinated group under ideal conditions, such as trial settings; and vaccine efficiency, the direct and indirect influence of vaccinations on the population in a real-life situation, are two classic metrics of vaccine impact. Estimating the extent of morbidity and mortality avoided is required to provide a numerical assessment of vaccination impact.

In many low- and middle-income countries (LMICs), vaccine provision is more difficult, as illustrated by the failure to make EPI vaccinations available to every child by 1990, regardless of environment. Other barriers to vaccine implementation include: underappreciation of the value of vaccines locally/regionally due to a lack of relevant data on disease burden, vaccine efficacy, or cost-effectiveness; insufficient healthcare infrastructure for vaccine handling, storage, programmatic management, and disease surveillance; and a lack of global, regional, or local policy-making and leadership. In 2018, 86 percent of children worldwide received three doses of DTaP, corresponding to 116,300,000 new-borns. Due to the combination of economic and political constraints, as well as varied access to non-governmental financing from Gavi, the Vaccine Alliance, vaccine coverage varies between low-, middle-, and high-income nations. Nonetheless the worldwide the global burden of disease study caused by vaccine-preventable infections has decreased, allowing many millions of children to live healthier lives. Another advantage of vaccination is evidence that, while vaccinations may not always prevent an infection, such as VZV or pertussis, they may result in a milder disease course.

Vaccines can protect people from diseases that aren’t caused by the infection they’re supposed to fight. Diseases with pathogens, especially viruses, can make you more susceptible to bacterial infections. For example, bacterial pneumonia and acute otitis media (OM), as well as Aspergillus pneumonia/pneumonitis, are common complications of influenza virus infection, both seasonal and pandemic. Secondary bacterial bronchopneumonia with S. pneumoniae, Streptococcus pyogenes, H. influenzae, and Staphylococcus aureus discovered at autopsy likely contributed to the excess mortality observed among healthy children and adults during the 1918–19 influenza pandemic. Influenza immunizations can help avoid these sequelae as well as morbidity in children, including acute OM; a systematic analysis found that influenza vaccine efficacy against OM is 51 percent (21–70 percent) in children. Furthermore, there is evidence that inactivated influenza vaccines given to pregnant women can reduce the number of newborns admitted to the hospital with acute respiratory diseases up to the age of six months. Infants (3 months) of HIV-negative pregnant women in South Africa were protected against hospitalisation with all-cause lower respiratory tract infections, including primary viral and secondary bacterial causes, with a vaccination effectiveness of 43% (p = 0.05). Additionally, in the United States, Spain, and South Africa, pneumococcal conjugate vaccines were found to lower the frequency of influenza-related hospital admissions in children by preventing subsequent bacterial infections following primary influenza infection.

Acknowledgement

None

Conflicts of Interest

The authors declare no conflict of interest.