Coronavirus pandemic | WHO chief scientist sees no herd immunity yet

Herd immunity is usually achieved through vaccination and occurs when most of a population is immune to a disease, blocking its continued spread.

PTI

July 24, 2020 / 16:00 IST

The chief scientist at the World Health Organization estimates that about 50 percent to 60 percent of the population will need to be immune to the coronavirus for there to be any protective “herd immunity” effect.

Herd immunity is usually achieved through vaccination and occurs when most of a population is immune to a disease, blocking its continued spread.

During a social media event on Friday, Dr Soumya Swaminathan said that studies done from some countries hit hard by COVID-19 show that about 5 percent to 10 percent of people now have antibodies, though in some countries, it has been as high as 20 percent.

She says: “As there are waves of this infection going through countries, people are going to develop antibodies and those people will hopefully be immune for sometime so they will also act as barriers and brakes to the spread."

Other experts have estimated that as much as 70 percent to 80 percent of the population need to have antibodies before there is any herd immunity effect.

COVID-19 Vaccine

Frequently Asked Questions

How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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