Passengers wearing face masks as a preventive measure against the spread of Covid-19 are seen on an escalator at Orlando International Airport.
Paul Hennessy | LightRocket | Getty Images
When the coronavirus pandemic broke out around the world in 2020, a number of governments and health officials seemed to be pinning their hopes on “herd immunity”.
This approach would cause the virus to spread through society and cause infection, but it would also create an immune response in those who have recovered.
If enough people received these antibodies – around 60-70% of the population – transmission of the virus would gradually decrease, and those who were not yet infected would be protected by the increasingly limited ability of the virus to spread.
That was the theory.
In reality, Covid-19 swept through Asia, Europe and America, causing millions of infections – from which millions of people recovered – but also hundreds of thousands of hospitalizations and deaths. To date, the virus has caused over 164 million infections and 3.4 million deaths worldwide.
The herd immunity strategy was quickly abandoned by most countries – with a few notable exceptions such as Sweden – and lockdowns became the main way to prevent the spread of Covid as vaccines developed rapidly.
Now we have highly effective vaccines and vaccination programs are advancing around the world. This has raised hope that once enough people in populations are vaccinated, herd immunity could be achieved – that is, if enough people are vaccinated, the virus has nowhere to go and become extinct.
But again, Covid-19 is proving unpredictable and we still don’t know how long the protection from vaccines or the natural immunity acquired from previous infections will last.
The hesitation of the vaccine, the role of children in transmission (infants are not eligible for vaccines) and most importantly the emergence of new variants of Covid around the world are also unknowns that could also prevent herd immunity, experts warn.
Most of them believe that Covid-19 will become endemic like the flu (meaning it will continue to circulate in parts of the population, likely as a seasonal threat) while hoping it will become less dangerous over time.
“Nowhere near herd immunity”
Epidemiologist Lauren Ancel Meyers, director of the University of Texas’ Covid-19 modeling consortium, described herd immunity as “the idea that if we vaccinate enough people around the world, the virus has nowhere to spread, and the pandemic will go away completely.” ” “”
“Unfortunately, we are very far from this reality worldwide,” she told CNBC.
“The virus continues to spread rapidly across many continents, more contagious varieties are emerging all the time that can potentially breach immunity, and many countries are lagging far behind the US in adopting vaccines.”
She noted that even in US cities there are critical areas of low immunity: “Where I live in Austin, Texas, we estimate the vaccination rate is between under 40% and over 80%, depending on the neighborhood in which you are Everywhere children under the age of 12 cannot be vaccinated. As long as there are pockets with low immunity, this secret virus will continue to spread and produce new variants. “
Even so, Meyers noted that “vaccines can help us get to a place where Covid-19 is a significantly less lethal threat,” even if we fail to achieve full herd immunity.
According to Meyers, there has been a lot of misinformation and misunderstanding about the herd immunity threshold. “Put simply, the herd immunity threshold is the percentage of the population that needs to be immunized before the virus goes away. In the real world, however, this is complicated.”
“With variants and low-vaccination bags emerging, there is no guarantee we will get there,” she said, noting the importance of people realizing, “The more people vaccinate, the faster the threat will fade . “
“We may never reach herd immunity and completely eradicate the virus on a global scale. However, that doesn’t mean we won’t return to a sense of normality anytime soon. We are already seeing the number of new cases and hospitalizations falling,” added Meyers added.
After a year, the coronavirus has experienced some significant mutations and a number of variants have become dominant due to their increased transmissibility – like those first detected in the UK and South Africa last year.
Now a variant first discovered in India in October 2020 is raging across the country and beyond. As with previous mutations, experts are investigating whether it could make it more transmissible (early evidence suggests), more lethal (early evidence suggests), and Covid vaccines less effective (early evidence suggests).
Professor Lawrence Young, a virologist at the University of Warwick Medical School in the UK, told CNBC that the pursuit of herd immunity in relation to Covid-19 is unlikely to be achievable.
“The pursuit of herd immunity in terms of people getting infected and then recovering is not great, as Sars-Cov-2 obviously has people getting sick – but it’s also about what the herd immunity threshold is and what percentage of it Population would they need to be protected? And that depends so much on the transmittability of the virus, “noted Young.
“We are dealing with variants that have different spreading abilities and I think that makes it quite difficult to achieve herd immunity or to rely on herd immunity.”
He emphasized that there are still many “unknowns” about Covid-19.
“And I think it’s going to be impossible to get herd immunity through vaccination. Variants and the fact that you don’t necessarily get lifelong immune protection after vaccination make it more difficult,” Young said.
When asked if there is any chance the coronavirus could be eradicated, Young said, “It won’t happen.”
“We’re going to have to live with it, like the flu, and we just have to get so many people vaccinated to keep them from getting sick.”