How is herd immunity impossible to defeat COVID-19?

American experts so far viewed that COVI -19 is even subject to herd immunity due to vast number of the infected. 
July 09, 2020 | 22:53
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Experts regarded the idea of herd immunity seems impossible, especially when maintaining antibodies to those who have had Covid-19 or have been vaccinated is unknown.

Herd immunity's possibility

On June 26, Dr. Anthony Fauci announced it's "unlikely" that a COVID - 19 vaccine with 70-75% efficacy taken by two-thirds of Americans can provide herd immunity to the SARS-CoV-2 coronavirus, ABC News reported.

A leading Chinese disease control expert has claimed that it would be 'completely impossible' for the world to combat the coronavirus pandemic with 'herd immunity'. Dr. Zhang Wenhong, who has led Shanghai's fight against COVID-19, said the method would lead to a 'global disaster that nobody wants to see', according to Daily Mail.

A Spanish study recently has cast doubt on the feasibility of herd immunity as a way of tackling the coronavirus pandemic. The study of more than 60,000 people estimates that around just 5% of the Spanish population has developed antibodies, BBC reported.

According to the report, "This cannot be achieved without accepting the collateral damage of many deaths in the susceptible population and overburdening of health systems. In this situation, social distance measures and efforts to identify and isolate new cases and their contacts are imperative for future epidemic control."

The method, then, would require at least half of the world's 7.8billion people to contract the virus to build up a global tolerance strong enough to stop the disease circulating, said Dr. Zhang, which turns out to be very unlikely.

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The first patient enrolled in Pfizer's COVID-19 coronavirus vaccine clinical trial at the University of Maryland School of Medicine in Baltimore, receives an injection. Photo: ABC News

How herd immunity works?

Herd immunity is a situation in which so many people have become immune to an illness - either by having it or by getting a vaccine - that it can no longer spread.

There are two paths to herd immunity for COVID 19 — vaccines and infection. While Chinese expert expects an effective vaccine by global cooperation, Dr. Fauci highlighted three factors determining its usage.

First is the vaccine's efficacy -- for example, the measles vaccine is 97-98% effective. Dr. Fauci believes that for COVID-19, we are unlikely to get a vaccine that is more than 75% effective.

Second is the vaccine's prevalence of use -- this is where Dr. Fauci's concern about the anti-vaccine movement comes into play.

Third is the durability and longevity of the vaccine's induced antibody immuno-response. This is where the two-month to three-month life span of antibodies becomes a concern, explained ABC News.

Sweden is one of the few countries in the world that haven't ordered a lockdown during the coronavirus pandemic in the hope of achieving herd immunity. However, a study in June showed only around 6.1 percent of Swedes had developed COVID-19 antibodies, well below levels deemed enough to achieve even partial herd immunity, according to Daily Mail.

Because about 70-90% of a population needs to be immune to protect the others, the prospects of herd immunity seem to struggle its effectiveness. There must be an available kind of vaccine to deal with this.

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