Collective immunity in America would be reached in 2023 10:34
(CNN) -
If you think herd immunity is the goal of this pandemic, it's time for a reality shower.
Herd immunity to covid-19 could come and go, scientists say.
Or we may never reach it.
"There are many things we have to do to get to herd immunity," said Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington.
But do not spread panic.
Here we explain why it is possible to get in and out of herd immunity, and what you can do now to maximize your chances of ending COVID-19 once and for all:
Why herd immunity is so difficult
"Herd immunity is the point where enough people have been infected or vaccinated that you basically can't maintain community transmission," Murray said.
"And if a case leads to less than one new infection, it eventually goes away."
Estimates vary on how much of the population needs to have immunity to reach that goal.
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Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, has said that herd immunity could be achieved if 70-85% of people are immune.
Dr. Jorge Rodríguez, a board certified internist, estimates the number to be approximately 85-90%.
"If we vaccinate 70% of the entire American population, including children, and then another 15-20% have already been infected, I think we are pretty close to normal with the virus," he said.
But there's a big problem: No one under the age of 16 can get a coronavirus vaccine in the United States right now.
The Pfizer / BioNTech vaccine is licensed for individuals 16 years of age and older, and the Moderna and Johnson & Johnson vaccines are licensed for adults 18 years of age and older.
All three vaccine manufacturers are conducting vaccine trials with children.
Some health experts say that middle and high school-age children could be vaccinated by this fall, but Fauci has said that younger children will likely have to wait until early 2022.
And that is a major obstacle to achieving herd immunity, since young people can still become infected and transmit the virus.
“We already have 25% of our population that is not eligible for the vaccine.
I mean, we're already starting with our hands tied, ”said epidemiologist Ali Mokdad, professor of health metrics sciences at IHME.
"That's why we want the people who are eligible for the vaccine, all of them, to take it."
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Anti-vaccines could impede herd immunity
One big reason we might never achieve herd immunity is because not enough people are willing to get vaccinated.
If that happens, the virus will have ample opportunities to spread, slowing down the return to normal life.
"It is important to vaccinate as many adults as possible as soon as possible," Rodríguez said.
"If you want the United States to open up, get vaccinated."
That includes young, healthy adults.
Not only can they be easy transmitters of the virus;
many also suffer from long-term complications, such as chronic fatigue, chest pain, shortness of breath, and mental confusion.
Still, about 20% of people surveyed said they would definitely not get vaccinated or would only get vaccinated if their work or school required it, according to the Kaiser Family Foundation's Covid-19 Vaccine Monitor.
About 29% of Republicans said they definitely would not get a vaccine, and 28% of white evangelical Christians said they definitely would not.
Rodríguez said he believes that doubt about vaccines would be reduced if everyone saw how badly the coronavirus can devastate victims.
“One of the reasons why I think many people do not believe in the severity of this infection is that it is different from cancer.
If you have a family member who has cancer, you see him go through the whole process.
You see them go through chemotherapy, you see them go through wilting… You see how horrible death is, ”he said.
“In covid, when a family member is ill, they are rushed to the hospital and never seen again.
They don't see him drowning in his own phlegm.
They don't see him gasping for air.
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Herd immunity can change depending on the season
Murray said he thinks the main reason we can "get in and out of herd immunity" is seasonality.
“Now we know that covid-19 is quite seasonal.
There is more potential for transmission in winter than in summer, ”he said.
“I think herd immunity can occur in the summer at pretty low levels, like 55%, 60%.
And I think that by winter, it will be closer to 80% immunity.
How might the seasons affect the amount of virus that spreads?
“Part of this may be the humidity.
Therefore, there is the idea that these respiratory viruses do not like humidity and because the outside air is cold (in winter), it becomes warm inside the house and therefore the relative humidity is lower. in the winter, ”Murray said.
"It could be the temperature itself - that the virus doesn't like hot temperatures, it likes cooler temperatures - in terms of how long it stays in the air or on surfaces."
But differences in seasonal transmission could also be due to human behavior, such as winter holiday celebrations and people gathering indoors because it's cold outside.
"Then there are some physical factors, and then there are definitely these behavioral factors," Murray said.
How would we know if we achieved herd immunity?
"That's going to be the tricky part," Murray said.
“What is going to happen, most likely in the summer, is that we will see very little transmission.
And I think everyone will say, 'It's time to celebrate!
It's over!'
And then sometime at the end of the year, it will be that critical period where many people may be surprised that the covid has returned.
And that's the tricky thing.
It is not so much about how we know that we are in herd immunity, but about how we anticipate that we are going to lose herd immunity.
It will be easier to see when we lose herd immunity, Murray said, because the covid-19 numbers will start to rise again.
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New (or future) variants could ruin herd immunity
Here's the good news: All three vaccines currently in use in the US provide strong protection against known variants of the coronavirus.
But as the virus continues to spread and replicate in new people, it has more opportunities to mutate.
And if there are significant mutations, new and more dangerous variants could emerge.
"The more replication there is, the more errors will occur," said Rodríguez.
Think of a virus as a necklace full of pearls of different colors.
There are maybe only eight colored pearls to choose from.
And in position number 1, you need a red pearl.
Position number 2 is a green pearl.
That is the genetic code, that sequence of pearl colors, "he said.
“When a virus replicates, it is supposed to make an exact replica of those pearl colors.
But every now and then, maybe a green pearl enters where a red one is supposed to be. "
The key is to nullify the amount of virus in circulation, so it has less chance of mutating and causing more infectious or deadly variants.
That's why getting vaccinated and keeping wearing masks is so important, Murray said.
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Traveling could make us lose herd immunity
Even if the US (or any other country) believes it has achieved herd immunity, global travel could present new variants and wreak havoc again.
That could be especially dangerous if a new variant compromises the effectiveness of vaccines or re-infects those who have previously been infected.
"Herd immunity will not happen until there is global immunity," Rodríguez said.
“The fact that we have herd immunity in the United States… as long as there is an influx of people from other countries and other areas, as long as there is an outflow of Americans going elsewhere, the chances of herd immunity not happening are great ».
And if a new variant spreads, whether by domestic or international travel, it could infect even non-travelers.
“There may be someone in my hometown in Miami who didn't get vaccinated.
And it is contagious.
And it is not a big problem (for him) because he is 30 years old and he is asymptomatic, "said Rodríguez.
But in his body it replicates (a variant).
And that new virus is resistant to all vaccines, and then you spread it to someone who is vaccinated, but it doesn't matter because this virus is resistant, and that person will get it.
This is the worst case.
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Immunity could wear off
Waning immunity, either from a previous infection or from vaccination, could be another reason the US could slip in and out of herd immunity.
"We don't know how long immunity to natural infections lasts," Rodríguez said.
“I have had patients who have been infected, and we check their antibodies a month later, and they are gone… I have had patients who have been infected in the first wave and they still have antibodies.
But it's very unpredictable, ”he said.
“Nor do we yet know how long we will have immunity after being vaccinated.
We do not know if it is a year.
We do not know if it is 9 months.
We do not know if it is 2 years.
Obviously, the people who participated in the studies (of the vaccine trial) that started in about October, are followed regularly ”to help determine how long the immunity of the vaccine lasts.
Murray said he suspects immunity from vaccination will outweigh immunity from infection.
"The question is how much," he said.
“If natural immunity (from infection) is declining, say, 20-30% over the course of a year or more, will a vaccine be only 10% (less effective)?
These are things we just don't know.
With two potential problems on the horizon - waning immunity and the possibility of new and more dangerous variants - Murray said many scientists believe that "people are going to end up getting vaccinated on a regular basis."
This would be similar to how people get a new flu shot each year.
Covid-19 "may exist forever, but it may not be as severe as it has been this time," he said.
"That is certainly the hope."
How to maximize our chances of ending covid-19
The most important step is to get vaccinated, Rodríguez said.
"By maximizing vaccines, we can minimize infectivity and mutations," he said.
"The more we vaccinate, the less likely we are (to enter and exit herd immunity) because there will be less replication."
Less replication means fewer opportunities for the virus to mutate into potentially dangerous variants.
“The virus only replicates when it infects someone.
The virus does not have the material to produce new viruses on its own, ”said Rodríguez.
"So, floating, a virus is not going to mutate."
After getting vaccinated, it is important "to still follow the recommendations of the CDC, because they will know what is happening in this country in terms of variants," he said.
"Now they know, that's why they say, 'Please keep wearing masks.'
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The best case and the most probable scenario
The best possible outcome is that the coronavirus "burns out just because so many people are vaccinated that they have nowhere to go," Rodríguez said.
"That is entirely possible."
But more realistically, due to vaccinations and other factors, Covid-19 will be with us for much longer, possibly in waves, Murray said.
He said that people can help prevent another seasonal increase next winter by wearing masks.
Wearing masks "really has a huge effect because if there is going to be transmission, it will be much less than what we have seen because many people will be vaccinated," he said.
"So it just takes a little more effort to bring the transmission to a halt."
Murray said that simple steps now can reduce the chances of losing herd immunity in the future.
“Anything that cuts the transmission will help reduce the appearance of new variants.
So definitely the vaccination and definitely the use of masks, "he said.
"I really think it depends a lot on how well we do to convince people to get vaccinated and how well we do to get vaccines to children once they are approved."
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The fate of covid-19 could range from returning every year to disappearing completely.
And the path it takes is largely in our power right now, Rodriguez said.
"Every day, every second, how long this is going to last is absolutely in our control, whether we are young or old, healthy or weak."
CNN's Paul LeBlanc contributed to this report.
Herd immunity