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What is herd immunity and will it affect the pandemic?

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The outbreak of disease caused by the new coronavirus has raised questions about a phenomenon known as "herd immunity" and whether it might play a role in how the pandemic progresses.

Here are some insights from infectious disease specialists:

WHAT IS HERD IMMUNITY?

Herd immunity refers to a situation where enough people in a population have immunity to an infection to be able to effectively stop that disease from spreading.

For herd immunity, it doesn't matter whether the immunity comes from vaccination, or from people having had the disease. The crucial thing is that they are immune.

With the new coronavirus infection -- called COVID-19 -- as more and more people become infected, there will be more people who recover and who are then immune to future infection.

"When about 70% of the population have been infected and recovered, the chances of outbreaks of the disease become much less because most people are resistant to infection," said Martin Hibberd, a professor of Emerging Infectious Disease at the London School of Hygiene & Tropical Medicine. "This is called herd immunity."

WILL IT AFFECT THE COVID-19 PANDEMIC?

With the new coronavirus outbreak, current evidence suggests that one infected person on average infects between two and three others. This means that, if no other measures are taken, herd immunity would kick in when between 50% and 70% of a population is immune.

"But it doesn't have to be –- and it won't be –- this way," said Matthew Baylis, a professor at the Institute of Infection, Veterinary and Ecological Sciences at Liverpool University.

By reducing the number of people that one person infects-- with social distancing measures such as closing schools, working from home, avoiding large gatherings and frequent hand washing -- the point at which herd immunity kicks in can be lowered.

"From an epidemiological point of view, the trick is to reduce the number of people we are in contact with ... so that we can drive down the number of contacts we infect, and herd immunity starts earlier," said Baylis.

The "sweet spot" he added, is when one infected person infects, on average, one or less than one other person.

© Thomson Reuters 2020.

©2020 GPlusMedia Inc.

7 Comments
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Where is the proof of herd immunity?

Not a single case is nentioned

Also, viruses continually mutate so even if it were a proven phenomenon, it would have little bearing on Nocov-19, a continually mutating virus...

-2 ( +2 / -4 )

There are many examples of herd immunity. One can look it up online. An example is the swine flu (aka Spanish Flu) epidemic of 1918 and 1919. A vaccine was never developed, but after two years the disease became much less widespread in the population.

I would like to point out that with the flu of 1918 and 1919, after a respite during the northern summer of 1918, it came back with a vengeance once the weather cooled off again. In fact, most fatalities occurred in 1919. In the end, somewhere around 4% of all the people on Earth died. If that happens again, we will see 300,000,000 fatalities.

2 ( +2 / -0 )

An example is the swine flu (aka Spanish Flu) epidemic of 1918 and 1919. A vaccine was never developed, but after two years the disease became much less widespread in the population.

Lots of people died though and with Covid-19 you potentially have 25% of people in intensive care being knocked off. That's a huge extra strain on hospitals and IC doctors have been the most vocal in urging people to take precautions. It's probably silently killing people in Japan as we speak, then Japanese people will carry it overseas later too. It's so irresponsible

theguardian.com/world/2020/mar/23/hospitals-likened-to-war-zones-as-doctors-prepare-to-make-grim-decisions

1 ( +1 / -0 )

2 medical experts discuss the virus. Some real interesting stuff here

https://www.youtube.com/watch?v=lWOYj8hjjjM

0 ( +0 / -0 )

Where is the proof of herd immunity?

Not a single case is nentioned

Do you ask for proof also for the microbial origin of infections? Herd immunity is a well characterized phenomenon described for infectious diseases after natural and man-made immunization. Countless cases can be found where outbreaks finish even if some percentage of people are still susceptible to infection.

Also, viruses continually mutate so even if it were a proven phenomenon, it would have little bearing on Nocov-19, a continually mutating virus.

That is irrelevant, RNA viruses mutate all the time, but vaccines still work against them because not all mutations alter the effect of antibodies, if you take a sample of Yellow Fever viruses from a single patient you would find dozens of variants with many different mutations, an all of them would be neutralized by a single vaccine.

2 ( +2 / -0 )

Where is the proof of herd immunity?

The concept is so well understood by everyone except vaccine maniacs that it doesn't have to supported with evidence every time it's mentioned. Just one of those things - like the speed of light, the age of the earth, evolution of humans, the structure of atoms, chemical composition of water, the electromagnetic spectrum, and similar schoolroom science great and small - that can be referred to without elaboration, and anyone who's not up to speed on the whether or why of it can (and should) look it up for themselves.

0 ( +1 / -1 )

I wonder how many anti-vaxxers are hoping for a covid19 vaccine. You certainly don’t here the anti-vaxxers voices these days.

1 ( +1 / -0 )

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