People hold hands on Fifth Avenue amid the coronavirus pandemic on April 10, 2021 in New York City.
Noam Galai | Getty Images Entertainment | Getty Images
As Covid vaccines develop around the world, many are looking forward to achieving ‘herd immunity’ – when the disease is no longer transmitted rapidly because most of the population is immune due to vaccinations or after being infected.
It is seen as a way to normalcy, and something that doctors and political leaders often discuss when talking about defeating Covid-19.
Although there are doubts about whether herd immunity is possible, medical experts who spoke to CNBC say it can be achieved. However, they point to a difficult path forward, as maintaining a high level of immunity will be a challenge.
“I think every part of the world will sooner or later reach herd immunity,” said Benjamin Cowling, head of the Department of Epidemiology and Biostatistics at the School of Public Health at the University of Hong Kong. Different communities can get there through vaccinations, infections or a combination of both, he added.
Not everyone agrees.
An article in the scientific journal Nature last month outlined five reasons why it is possible to achieve herd immunity. The report states that barriers to herd immunity include the following: new variants, declining immunity and questions about whether vaccines can prevent transmission.
Shweta Bansal, a mathematical biologist, told the publication: “Herd immunity is only relevant if we have a transmission-blocking vaccine. Failure to do so is the only way to increase herd immunity in the population. to give everyone the vaccine. “
Herd immunity: ‘complicated’ but possible
Health experts who spoke to CNBC acknowledge that the factors raised in the Nature article could hamper progress toward herd immunity – but said they believe it is still within reach.
“We’re not trying to eradicate it, we’re trying to stop out-of-control transmission from the community. In that sense, we can achieve (herd immunity),” said Dale Fisher, professor of infectious diseases at Yong Loo Lin National University. for Medicine in Singapore.
Dr. Anthony Fauci, chief medical adviser to President Joe Biden, said 75% to 85% of people should be vaccinated to create an “umbrella” of immunity that prevents the virus from spreading. Fisher estimates that figure is around 70%.
“Achieving … 70% is possible, but there are many threats to it,” he said, explaining that the percentage of a population immune to Covid-19 would decline if immunity weakened. makes the vaccines less effective.
“Herd immunity is something very beautiful and conceptual to strive for, but it’s more complicated than that,” he said during a call. “If you want to call a magic number of about 70%, all I’m saying is, it’s very difficult to achieve and maintain.”
Herd immunity may not be permanent, but it may be relatively short-term.
Benjamin Cowling
School of Public Health at the University of Hong Kong
Cowling agreed that there is ‘no guarantee’ that the level of immunity will remain high in the long run. “Herd immunity may not be permanent, it may be something that is relatively short-term,” he said.
After all, it is something the world can work on, he added, emphasizing that booster shots can help if there is a loss of protection.
Return to ‘normal’
It could take three to five years for the world to return to a ‘normal state’, said Carlos del Rio, a professor of medicine at Emory University School of Medicine.
“There are still a lot of broadcasts worldwide, and I think it’s going to take a while before that changes,” he told CNBC’s Street Signs Asia on Monday.
The World Health Organization warned this week that the pandemic was “growing exponentially” and more than 4.4 million new Covid-19 cases were reported last week.
Maria Van Kerkhove, technical leader of the agency for Covid-19, said the world had reached a ‘critical point of the pandemic’.
“Vaccinations and vaccinations are coming online, but it is not yet here in all parts of the world,” she added.
Fisher said the world is still ‘very vulnerable to major eruptions’, but cases could be sporadic within five or ten years. Meanwhile, there will be a transition period.
“Herd immunity is not a binary phenomenon,” he said. “Most people think you have it, or that you do not have it – but there is, of course, gray in between.”
Cowling said he thinks the biggest risk for Covid will be in the next 12 months, but the threat will diminish thereafter as vaccines are deployed.
“What I would expect in the coming years is that the virus will continue to spread, it will be endemic, but it will no longer pose a major health threat to the public,” he said.
CNBC’s Berkeley Lovelace contributed to this report.