Health officials around the world are vying to vaccinate enough people to stop the spread of COVID-19, but what is described as “sufficient” remains an open question.
The goal is to reach “herd immunity,” which is when there are enough people with immunity, either against vaccination or a past infection, to stop the uncontrolled spread.
Herd immunity does not make a person immune and outbreaks can still appear. It means that a virus no longer easily jumps from person to person, which helps protect those who are still vulnerable to catching it.
No one knows for sure what the herd’s immunity threshold for coronavirus is, although many experts say it is 70% or higher. And the emergence of variants further complicates the picture.
This is what is known about the herd and the immunity of the herd.
HOW IS THE LIMIT OF FIRST IMMUNITY CALCULATED?
It is a formula based on the infection that a virus has or the number of people who catch the virus from an infected person, on average.
But the calculation only offers a broad goal for when there can be a large drop in distribution. The figure may also vary by region.
“It’s not 64.9 it’s terrible and 70.1 is fantastic,” Dr. Walter Orenstein, expert in infectious diseases at Emory University.
Orenstein points out that vaccination levels and other factors that affect spread may differ even within a city.
HOW DO WE KNOW THAT WE HAVE REACHED IMMUNITY THAT WAY?
The evidence that we are approaching herd immunity would be a “disruption of the transmission chain,” Ashley St. said. John, who studies immune systems at Duke-NUS Medical School in Singapore.
But don’t expect any big statement to reach that milestone.
To determine if restrictions are needed, health officials will monitor trends in infection and hospitalization as vaccines are developed. And these decisions are likely to begin long before the ideal immunity threshold in the herd is reached, although they will be gradual and vary by region.
In India, for example, scientists believe more people will need to be protected in densely populated cities, where the virus spreads faster than in its vast countryside.
India plans to look for antibodies in people nationwide to find out what percentage of its nearly 1.4 billion people have already become infected, said Dr Jayaprakash Muliyil, who advises the government on virus surveillance.
The effectiveness of vaccines also plays an important role. Fewer people should be vaccinated to achieve herd immunity if the shots are more effective.
HOW DO YOU AFFECT CORONAVIRUS VARIANTS TO RAMADA IMMUNITY?
It depends on the protection provided by the infection or vaccination passed against the variant.
If vaccines are significantly less effective against a variant, an even larger part of the population should be vaccinated or existing vaccines should be upgraded. to make them more effective, Orenstein said.
So far, it seems that the features provide at least some protection against the most worrying variants. But scientists are still studying the situation and are worried about other mutations.
Variants have stressed the importance of vaccinating people as quickly as possible. Slow transmission is critical, as viruses can mutate when they infect people.
SHOULD HERD IMMUNITY BE GLOBAL?
Global herd immunity is ideal but unlikely.
Wealthy nations have reserved most of the vaccines that will be manufactured this year. In the U.S., for example, officials have said enough people could be vaccinated in the fall to start returning to normal.
But many poorer countries are likely to have to wait longer. That is why the World Health Organization has warned global herd immunity is unlikely to be achieved this year.
Differences in vaccination levels between countries are also the reason why many experts believe the virus will never be completely eliminated.
CAN IMMUNITY BE DISAPPOINTED?
It is not known how long immunity lasts, either after vaccination or an infection, although experts believe it should take at least a few months.
However, reinforcements may be needed on the road. And while current COVID-19 vaccines are expected to work on variants identified in the UK and elsewhere, it is possible that the virus may mutate enough over time to update the photos.
Mutations in flu viruses, for example, are the reasons we get flu shots every year. But experts note that coronaviruses generally do not mutate as easily.
WHAT IF COVID-19 VACCINES DO NOT PREVENT INFECTION?
The COVID-19 vaccines that are being introduced now seem to be very effective in preventing people from getting sick. We don’t know yet which are good for completely stopping the infection, but should help reduce the spread of the virus.
This is because vaccines prevent the virus from multiplying in the body. So even if you get infected after the vaccination, your body should shed fewer viruses and for a shorter time, said Deborah Fuller, a vaccination expert at the University of Washington.
Another reason why vaccinating as many people as possible is key to ending the pandemic.
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