What Is Herd Immunity? A Scientist & Researcher Explain
The term group immunity it means that a sufficient population has gained immunity to quell the spread of a pathogen. You can think of herd immunity as something similar to fire starting in a field – if the field is dry and full of weeds, the fire will ignite and spread rapidly. However, if the field is well maintained with watering and pruning, the fire will go out. Future embers that may land there will be much less likely to ignite.
The embers look a lot like SARS-CoV-2, the coronavirus that causes COVID-19.
Theoretically, herd immunity can be achieved either by infection and recovery or by vaccination. The danger in trying to achieve herd immunity through infection is that many people will die or be forced to live with post-recovery disabilities. Furthermore, research has shown that the immune response resulting from infection does not always provide sufficiently strong long-term protection against COVID-19 and its evolving strains. Therefore, public health experts still recommend vaccination against coronavirus to achieve the strongest and most reliable protection.
When the COVID-19 pandemic broke out, scientists quickly began developing vaccines so that populations could build immunity to slow the spread of coronavirus like fire. Meanwhile, nearly every country required or encouraged social distancing, masking, and other public health measures.
Unfortunately, the disjointed implementation of these efforts, coupled with large-scale surges and the appearance of the highly transmissible delta variant, has forced public health experts to recalculate what it would take to achieve “herd immunity” to COVID-19.
Why Herd Immunity Is Important
Previous experience with respiratory pathogens that were comparable to the novel coronavirus allowed public health experts to make informed estimates of what it would take to reach the lower threshold of herd immunity for COVID-19. They initially believed that around 70% of the population would need to be vaccinated to effectively slow or stop the spread of SARS-CoV-2.
But with the delta variant continuing to spread rapidly around the world, experts revised that estimate. Now epidemiologists and other public health officials estimate that about 90% of the U.S. population would need to be vaccinated to achieve herd immunity for COVID-19.
Virus like those that cause polio and measles required decades of education and vaccination programs to achieve herd immunity and ultimately eliminate them in the US But since new cases of COVID-19 in the US. continue to count in the tens of thousands daily, it is clear that COVID-19 is going to stay.
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There are several reasons why it will take some time to achieve herd immunity to COVID-19. COVID-19 vaccines are currently authorized for some age groups but not others. In perspective, about 90% of the US population. get the measles, mumps, and rubella vaccine, or MMR – of children, and 93% of the population is vaccinated against polio; both have been routine childhood immunizations for decades. Since children make up more than 20% of US residents, the country may not be able to achieve herd immunity against COVID-19 without widespread childhood vaccination, even if all eligible adults were vaccinated.
As of November 1, 2021, only 67.8% of the total US population Ages 12 and up eligible for the vaccine had been fully vaccinated. Experts have attributed this to multiple factors including vaccine hesitation and the politicization of the pandemic.
Of course, no vaccine is perfect. Vaccinated people may have breakthrough infections, although COVID-19 vaccines continue to be effective reduce the most severe cases of COVID-19. Additionally, research suggests that those who experience COVID-19 after vaccination can transmit the virus at lower transmission rates than those who are not vaccinated.
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