Collective immunity, or as some experts now call it, “population” or “community” immunity, is when most of the population is immune to a particular disease, whether through natural infection or through vaccination. When a population reaches this stage, the virus has nowhere to go and the disease goes away. Then even people who do not have individual immunity are protected.
As with any disease, the number of people who need to be immunized to protect the community depends on how infected it is. For Covid-19, experts believe the magic number could be between 70 and 90% of a population immune to the virus. The world is far from this level.
“Given where we are today, as we look around the United States and when we look around the globe, it looks like that won’t happen for the foreseeable future,” said Lauren Ancel Meyers, Managing Director of Covid-19. Modeling Consortium at the University of Texas at Austin.
That’s a good goal, Meyers said, but she checks off a host of factors in this particular pandemic that suggest the odds are not in her favor: vaccinating so many people would be nearly impossible; this particular virus spreads too quickly; more contagious variants threaten to make vaccines less effective; there are whole countries and pockets of the United States that have few fully vaccinated people; there are issues of access to vaccines and equity; children are not yet vaccinated; and about a quarter of the population hesitate or refuse to be vaccinated.
“We know how fast this virus is spreading and how stealthily. We would really need to get a lot of people vaccinated before we can eradicate this virus,” Meyers said.
However, Dr Bill Hanage, an epidemiologist at Harvard TH Chan School of Public Health, said few infectious diseases were becoming extinct in the world.
“We really only eradicated smallpox and if there hadn’t been a few more interventions beyond vaccines, even that could still have been with us,” Hanage said. “Most people who know anything about infectious diseases don’t think total eradication is possible.”
But all is not lost. The world does not have to live in lockdown forever.
In Israel, for example, once around 50-55% of the population was vaccinated, cases dropped dramatically.
“We can probably get enough immunity in the population where the virus is not a major threat everywhere,” Hanage said. Public health officials will need to watch for cases and variants in the fall, but he believes people can return to some level of normal behavior anyway. “We will get there eventually, and I hope it will be through vaccination rather than infection, because infection can kill people,” he said.
In the United States, more than 40% of adults are fully vaccinated, according to data released Monday by the United States Centers for Disease Control and Prevention. The number of new cases is down 15% from last week, but the United States still averages 49,209 cases per day over the past seven days.
If ever the number of cases gets low enough, even without herd immunity, said Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases last Sunday, the country will begin to move towards “normalcy”.
“It won’t be like a light switch on and off – we’re going from where we are now to completely normal. It’s going to be gradual,” Fauci told CNN’s Jim Acosta. “Little by little you will see this. Approaching normal.”
It is not known exactly how many people will need to be vaccinated to get closer to normal, Fauci said. “I can’t tell you what that exact number is now, because we don’t know,” he said.
If the cases are low enough, Covid-19 becomes manageable.
“We may not get to zero. We probably won’t,” Dr. Ashish Jha, dean of Brown University School of Health, told CNN’s New Day on Monday. “But if we can get the infections at very low levels, most of us can get on with our lives as normal. I think we can probably live with that.”
The way to get back to normal is to continue testing, monitoring for variants, and getting as many people vaccinated as possible as quickly as possible. Vaccines protect the individual and protect against the spread of variants.
“The more people get vaccinated, the fewer variants there are. You don’t want to see this disease develop a selective advantage that will make them more contagious and then mutate in a way that makes vaccines ineffective or makes this disease more deadly,” said Dr Claudia Hoyen, an infectious disease and molecular epidemiologist with University Hospitals at Cleveland Medical Center.
Hoyen said the country is in a much better situation than three months ago as large numbers of vulnerable people have been vaccinated. “But again, we always have to be sure that the end of the game is to try and stop this if we can,” Hoyen said.
Immunization rates are slowing.
“Every 1% from now on will represent incredible progress for the country,” Andy Slavitt, a senior official on the White House coronavirus response team, told CNN.
This is why states and the Biden administration began to focus on enticing and encouraging people to get vaccinated.
“I think we’re going to need a lot more of that kind of effort – getting the vaccine to people, building trust with communities,” said Samuel Scarpino, assistant professor who heads the Emerging Outbreaks Lab at Northeastern University. .
In Israel, he said, vaccinators went to a bar that picked up people’s tabs if they got vaccinated. New Jersey has just launched “Shot and a Beer,” a campaign that offers free beer to adults who present their completed CDC vaccination card at participating breweries.
“I was joking that you could offer to let tourists cut the long lobster lines in Maine in the summer if they got vaccinated,” Scarpino said.
“I think if we take that kind of attitude and distribute enough vaccines to people, we could reach the right level to turn this serious disease that has been completely debilitating from a societal and economic point of view, into something. something that is not eradicated, but it is something closer to the common cold, which becomes more manageable. ”
CNN’s Ryan Prior, Jeremy Diamond, Kaitlan Collins and Laura Ly contributed to this report