You can reach herd immunity and lose it. repetition.

Here’s what you can do to prevent this:

First Edition: March 30th, 21st, 17:34 ET

Updated: March 30th 21 19:17 ET

Holly Yang, CNN

(CNN) — If herd immunity seems to be the final stage of this pandemic, it’s time to check the reality.

According to scientists, herd immunity with Covid-19 can come and go. Or it may not reach at all.

Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, said:

But don’t panic. This is why it is possible to soak in and out of herd immunity, and what we can do now to maximize the chances of permanently sniffing Covid-19.

Why herd immunity is so difficult

“Herd immunity is basically a condition in which there are enough people infected or vaccinated to maintain an infection in the community,” Murray said.

“And if one case leads to less than one new infection, it will eventually disappear.”

Estimates depend on how many people need to be immune to reach that goal.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said: May reach herd immunity If 70-85% of people are immune. Dr. Jorge Rodriguez, a board-certified physician, estimates that number is about 85-90%.

“If 70% of the total population of the United States, including children, is vaccinated and another 15-20% are already infected, I think the virus is almost normal,” he said.

But there is a big problem. Currently, people under the age of 16 are not vaccinated against the coronavirus vaccine in the United States. The Pfizer / BioNTech vaccine is licensed for ages 16 and older, and the Moderna and Johnson & Johnson vaccines are licensed for adults ages 18 and older.

All three vaccine manufacturers are conducting vaccine trials in children.Some health experts say high school and junior high school children could be vaccinated by this fall, Fauci said. Younger children will probably have to wait until early 2022..

And it is a major obstacle to reaching herd immunity. Because young people can still get infected and get the virus.

“We are already 25% of the population out of the vaccine, which means we have already started (hand in hand),” said epidemiologist Arimokdad, a professor of health measurement science at IHME. ..

“That’s why I want everyone to be vaccinated, that is, everyone to be vaccinated.”

Anti-vaxxers can prevent group immunity

A major reason we may not reach herd immunity is that a sufficient number of people are willing to be vaccinated.

If that happens, the virus has ample opportunity to spread and delays the return to normal life.

“It is important to vaccinate as many adults as possible,” Rodriguez said. “If you want to open up America, get vaccinated.”

This includes young and healthy adults. Not only do they become simple senders of the virus, but many also suffer from long-term complications such as chronic fatigue, chest pain, shortness of breath, and brain fog.

Still, according to the Kaiser Family Foundation, about 20% of those surveyed say they will never be vaccinated or will only be vaccinated when needed at work or school. COVID-19 Vaccine Monitor..

About 29% of Republicans They definitely said they wouldn’t vaccinate, And 28% of white evangelical Christians say they will never do so.

Rodriguez said he believes that vaccine hesitation will be reduced if everyone sees how badly the coronavirus destroys victims.

“One of the reasons many people don’t believe in the severity of this infection is different from cancer. If you have a family with cancer, you want them to go through the entire process. You’ll see. You see them going through chemotherapy, you see them going through wilting … You’ll see how terrifying death is, “he said.

“In Covid, when a family gets sick, they are taken to the hospital and never meet again. You never see them drowning in their own sputum. Seeing them out of breath there is no.”

Herd immunity can change from season to season

Murray said he believes that seasonality is the number one reason we can “go in and out of herd immunity.”

“We now know that Covid-19 is fairly seasonal. It’s more likely to get infected in winter than in summer,” he said.

“I think herd immunity can occur at fairly low levels, such as 55% and 60% in the summer, and in the winter it approaches 80% immunity.”

How does the season affect the spread of the virus?

“Some of them may be humidity. Therefore, the idea is that these respiratory viruses dislike humidity, and because the outside air is cold (in winter), the inside of the house gets hot and the relative humidity gets low in winter. “I will,” said Murray.

“The temperature itself can be the temperature itself, in terms of the amount of time the virus is hanging in the air or on the surface. The virus does not like warm temperatures. It prefers cold temperatures.”

However, seasonal differences in communication can also be due to human behavior, such as winter holiday celebrations or people gathering indoors due to the cold outside.

“So there are some physical factors, and definitely these behavioral factors,” Murray said.

How can I tell if I have reached herd immunity?

“It will be a difficult part,” Murray said. “The most likely thing that happens in the summer is that there are few infections, and I think everyone will say,’Celebration time! It’s over!’

“And sometime later this year will be that important time when many may be surprised by the return of Covid. And that’s tricky. We’re in herd immunity. How you know that is not so important, it is how we predict that we will drop out of herd immunity. “

Drop it to make it easier to see Out Group immunity Murray said as the number of Covid-19 began to skyrocket again.

New (or future) variants can ruin herd immunity

This is good news. All three vaccines currently used in the United States provide strong protection against known variants of the coronavirus.

However, as the virus continues to spread and is replicated to new people, it has more opportunities to mutate. And if there is a significant mutation, new and more dangerous mutations can emerge.

“The more duplicates, the more mistakes we make,” Rodriguez said.

“Think of the virus as a necklace full of beads of different colors. You can probably choose from eight colored beads. And position No. 1 requires red beads. Position No. 2 Is a green bead. It’s a genetic code, a sequence of bead colors, “he said.

“When the virus replicates, it is supposed to make an exact copy of the color of those beads. But sometimes, green beads may go where red beads should be.”

The important thing is to crush the amount of virus that is circulating. Therefore, it is less likely to mutate and cause an infectious or fatal mutation.

That’s why it’s so important to be vaccinated and keep wearing a mask, Murray said.

Travel can drop us from herd immunity

Even if the United States (or any other country) believes it has reached herd immunity, world travel can introduce new variants and cause havoc again.

This is especially dangerous if the new variant compromises the effectiveness of the vaccine or re-infects a previously infected person.

“Herd immunity does not occur until global immunity is obtained,” Rodriguez said.

“Just because we have herd immunity in the United States … as long as there is an influx of people from other countries and regions, and as long as there is an outflow of Americans going elsewhere, herd immunity will occur. It’s very likely not. “

Also, if a new variant spreads from either overseas or domestic travel, it can be transmitted to non-travelers.

“There may be one person in my hometown of Miami who wasn’t vaccinated, and he gets it, because he’s asymptomatic at age 30. It’s not a big deal (for him), “said Rodriguez.

“But it replicates in his body (a variant). And the new virus is resistant to all vaccines, and he spreads it to vaccinated people, but this virus It doesn’t matter because it’s tolerant. And that person gets it. This is the absolute worst scenario. “

Immunity can wear out

The weakening of immunity from previous infections or vaccinations may be another reason the United States may enter and leave herd immunity.

“I don’t know how long the immunity from a natural infection will last,” Rodriguez said.

“I had an infected patient who checked for antibodies a month later and they left … there were patients infected with the first surge, but they still have antibodies, but It’s very unpredictable, “he said.

“I still don’t know how long I’ll be immunized from vaccination. I don’t know if it’s a year. I don’t know if it’s 9 months. I don’t know if it’s still 2 years. Obviously. People who participated in the (vaccine trial) study, which began in October or so, are regularly followed up, “helping determine how long vaccine immunity lasts.

Murray said vaccination immunity is superior to infection immunity.

“How good is the problem,” he said. “If the innate immunity (due to infection) is weakened, for example 20-30% over a year or more, is the vaccine only 10% (less effective)? These are things we don’t know. is.”

Many scientists say, “People are vaccinated regularly,” Murray said, as two potential problems are imminent: weakened immunity and the potential for more dangerous new variants. I believe it will be. “

This is similar to how people get a new flu shot each year.

Covid-19 “may exist forever, but it may not be as serious as this time,” he said. “That is certainly hope.”

How to maximize the chances of crushing Covid-19

According to Rodriguez, the most important step is to get vaccinated.

“Maximizing vaccination can minimize infectivity and mutations,” he said.

“The more vaccinated you are, the less replication you have and the less likely you are to get in and out of herd immunity.”

Less replication means less chance of the virus mutating into a potentially dangerous variant.

“The virus only replicates when it infects someone. The virus itself has no material to make a new virus,” Rodriguez said. “So the virus isn’t going to mutate because it’s floating.”

Even after being vaccinated, “the CDC knows even the varieties of what’s happening in this country, so it’s important to follow the CDC’s recommendations,” he said.

“They know now, so they’re saying,’Keep wearing the mask.'”

Best scenario and more likely scenario

The best possible result is that the coronavirus “burns out because there are so many people who have been vaccinated and have nowhere to go.” “It’s completely possible.”

But more realistically, due to vaccine hesitation and other factors, Covid-19 will be much longer and probably with us like a wave, Murray said.

He said wearing masks can help people prevent another seasonal surge next winter.

Masking “has a huge effect, because when an infection occurs, so many people are vaccinated, which is far less than we’ve ever seen,” he said.

“Therefore, it takes a bit of work to stop sending on the track.”

Murray said simple steps can reduce the chances of losing herd immunity in the future.

“Everything that reduces infection helps reduce the emergence of new variants, so definitely vaccination, and definitely wearing a mask,” he said.

“I think it depends a lot on how well it works to convince people to get the vaccine and how well it works to deliver the vaccine to the children once they are approved.”

The fate of Covid-19 may range from returning each year to being completely wiped out. And the route it takes is now largely in our power, Rodriguez said.

“Every day, every second, how long this lasts is absolutely in all our controls, whether we are young or old, healthy or weak.”

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