This is the fourth essay in a series that has been coming out at roughly two-month intervals since the outbreak of the pandemic. Six months ago, populations across the world acquiesced, with minimal debate, to lockdowns to fight the Covid pandemic. Amid confusion and horrifying death tolls, the default position was to protect the elderly and minimize loss of life. Now the question is different. In the U.
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General Public Engagement. Dr Manish Sadarangani explains how herd immunity works and why vaccinating children is important. Manish Sadarangani : Herd immunity describes how a population is protected from a disease after vaccination by stopping the germ responsible for the infection being transmitted between people. In this way even people who cannot be vaccinated can be protected. In most people the bacteria live harmlessly in the throat and do not causes disease, but sometimes they get into the bloodstream leading to these severe infections.
W hen, along with applied systems scientist Dr Joe Norman, we first reacted to coronavirus on 25 January with the publication of an academic note urging caution, the virus had reportedly infected fewer than 2, people worldwide and fewer than 60 people were dead. That number need not have been so high. At the time of writing, the numbers are , and 15, respectively. Our research did not use any complicated model with a vast number of variables, no more than someone watching an avalanche heading in their direction calls for complicated statistical models to see if they need to get out of the way. We called for a simple exercise of the precautionary principle in a domain where it mattered: interconnected complex systems have some attributes that allow some things to cascade out of control, delivering extreme outcomes.
Herd immunity also called herd effect , community immunity , or population immunity is a form of indirect protection from infectious disease that can occur with some diseases when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity. Individuals can become immune by recovering from an earlier infection or through vaccination. Herd immunity was recognized as a naturally occurring phenomenon in the s when it was observed that after a significant number of children had become immune to measles , the number of new infections temporarily decreased, including among the unvaccinated. The exact herd immunity threshold HIT varies depending on the basic reproduction number of the disease.