How Will We Know When We Reach Herd Immunity?
2021-02-26
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1How will we know when we reach herd immunity?
2That is the question people are asking as governments race to vaccinate people around the world to stop the spread of COVID-19.
3Herd immunity is when a large number of people in a community will either have recovered from infection or been vaccinated.
4Herd immunity does not mean everyone is protected from the virus.
5It means that the coronavirus can no longer spread easily, helping to protect those who are at risk.
6Once people are sick or receive the vaccine, they start to develop antibodies.
7Experts think the number of people with antibodies needs to reach 70 percent or more for herd immunity.
8However, the virus is always changing and developing into new variants.
9Health officials are now concerned with variants first discovered in Britain, South Africa and Brazil spreading around the world.
10How do you calculate the percentage of people who need to be immune?
11Finding how many people, on average, catch the virus from one infected person is important to understanding herd immunity.
12Dr. Walter Orenstein is an infectious disease expert at Emory University.
13He said the percentage of people who need to be immune depends on a number of things.
14The number could be different depending on where you live.
15But it is not an exact number.
16"It's not 64.9 is terrible and 70.1 is fantastic," he said.
17How do we know when we have reached herd immunity?
18Experts say there will not be a big announcement.
19The evidence will come when there is a large decrease in new infections and fewer people need to go to the hospital for treatment.
20The numbers will be different depending on what part of the world you are in.
21For example, in India, scientists believe more people will need to be protected from the virus in cities than those who live in rural areas.
22The virus spreads easier and faster in densely populated cities.
23India is working to find out how many of its 1.4 billion people already have recovered from the virus.
24And if current vaccines work well against the virus, fewer people will need to be vaccinated to reach herd immunity.
25How will the virus variants affect herd immunity?
26If vaccines or antibodies from past infections protect people from getting sick again, the fast-spreading variants are not a big concern.
27However, if current vaccines are less effective against the variants, drug makers will have to update the shots to make them more effective.
28And even more people will need to be vaccinated.
29Scientists are also worried about vaccinating people as quickly as possible to prevent new variants from developing.
30Does herd immunity need to be global?
31Yes, it is important to reach herd immunity around the world.
32But some parts of the world will struggle with the coronavirus longer than in others.
33The World Health Organization said herd immunity will probably not happen around the world this year.
34That is because rich nations have reserved most of the vaccines that will be produced in 2021.
35Poor countries will have to wait longer.
36Experts say the virus will never completely come to an end because different countries will have different vaccination levels.
37Can herd immunity wear off?
38Experts think immunity from earlier infection or a vaccine should last several months.
39But it is likely we will need follow-up shots, known as boosters, in the future.
40The seasonal flu viruses are changing all the time.
41That is why people need a flu shot each year.
42The coronavirus is also changing but not as easily.
43So it is possible people will probably not need a COVID-19 shot every year.
44What if the vaccines do not keep people from getting sick?
45The current vaccines, from Pfizer-BioNTech and Moderna, seem to work very well.
46They do prevent people from getting sick.
47It is not clear, however, how well they stop the virus from moving from person to person.
48But experts say they should help to reduce the spread of the virus.
49Deborah Fuller is a vaccine expert at the University of Washington.
50She said the vaccines should limit the amount of time people can spread the virus to others if they do get sick.
51I'm Dan Friedell.
1How will we know when we reach herd immunity? 2That is the question people are asking as governments race to vaccinate people around the world to stop the spread of COVID-19. 3Herd immunity is when a large number of people in a community will either have recovered from infection or been vaccinated. Herd immunity does not mean everyone is protected from the virus. It means that the coronavirus can no longer spread easily, helping to protect those who are at risk. 4Once people are sick or receive the vaccine, they start to develop antibodies. Experts think the number of people with antibodies needs to reach 70 percent or more for herd immunity. 5However, the virus is always changing and developing into new variants. Health officials are now concerned with variants first discovered in Britain, South Africa and Brazil spreading around the world. 6How do you calculate the percentage of people who need to be immune? 7Finding how many people, on average, catch the virus from one infected person is important to understanding herd immunity. 8Dr. Walter Orenstein is an infectious disease expert at Emory University. He said the percentage of people who need to be immune depends on a number of things. The number could be different depending on where you live. But it is not an exact number. 9"It's not 64.9 is terrible and 70.1 is fantastic," he said. 10How do we know when we have reached herd immunity? 11Experts say there will not be a big announcement. 12The evidence will come when there is a large decrease in new infections and fewer people need to go to the hospital for treatment. 13The numbers will be different depending on what part of the world you are in. 14For example, in India, scientists believe more people will need to be protected from the virus in cities than those who live in rural areas. The virus spreads easier and faster in densely populated cities. 15India is working to find out how many of its 1.4 billion people already have recovered from the virus. And if current vaccines work well against the virus, fewer people will need to be vaccinated to reach herd immunity. 16How will the virus variants affect herd immunity? 17If vaccines or antibodies from past infections protect people from getting sick again, the fast-spreading variants are not a big concern. 18However, if current vaccines are less effective against the variants, drug makers will have to update the shots to make them more effective. And even more people will need to be vaccinated. 19Scientists are also worried about vaccinating people as quickly as possible to prevent new variants from developing. 20Does herd immunity need to be global? 21Yes, it is important to reach herd immunity around the world. But some parts of the world will struggle with the coronavirus longer than in others. 22The World Health Organization said herd immunity will probably not happen around the world this year. That is because rich nations have reserved most of the vaccines that will be produced in 2021. Poor countries will have to wait longer. 23Experts say the virus will never completely come to an end because different countries will have different vaccination levels. 24Can herd immunity wear off? 25Experts think immunity from earlier infection or a vaccine should last several months. But it is likely we will need follow-up shots, known as boosters, in the future. 26The seasonal flu viruses are changing all the time. That is why people need a flu shot each year. The coronavirus is also changing but not as easily. So it is possible people will probably not need a COVID-19 shot every year. 27What if the vaccines do not keep people from getting sick? 28The current vaccines, from Pfizer-BioNTech and Moderna, seem to work very well. They do prevent people from getting sick. 29It is not clear, however, how well they stop the virus from moving from person to person. But experts say they should help to reduce the spread of the virus. 30Deborah Fuller is a vaccine expert at the University of Washington. She said the vaccines should limit the amount of time people can spread the virus to others if they do get sick. 31I'm Dan Friedell. 32Candice Choi and Aniruddah Ghosal wrote this story for The Associated Press. Dan Friedell adapted it for Learning English. Hai Do was the editor. 33Do you understand the meaning of herd immunity? We want to hear from you. Write to us in the Comments Section and visit our Facebook page. 34_______________________________________________________________ 35Words in This Story 36variant - n. something that is different in some way from others of the same kind 37immunity - n. the power to keep yourself from being affected by a disease 38antibody - n. a substance produced by the body to fight disease 39update - v. to change (something) by including the most recent information 40flu - n. a common disease that is caused by a virus and that causes fever, weakness, body aches, and breathing problems