The brand new, stunningly effective Covid-19 vaccines were rolling out across the country this time last year, injecting a strong note of optimism into the US’ once stumbling pandemic response.
Hundreds of thousands of people were queuing every day to get their shots. We were tracking a new number: the percentage of Americans who had been vaccinated, rather than the steady drumbeat of cases, hospitalizations, and deaths. We believed that this number represented our best chance of surviving the virus.
The United States was caught up in a fever dream of achieving herd immunity, a point at which vulnerable individuals, such as those who were too young to be vaccinated or who didn’t respond well to vaccines, might be protected anyway because, as a community, we would weave an invisible safety net around them.
If someone is infected by a virus, they will be surrounded by enough people who are immune to infection that the virus will have nowhere to go. It is unable to spread.
We had reached this point in our fight against some formidable viruses, such as rubella and measles, as a country. With Covid-19, we thought we’d be able to get there. We were most likely mistaken.
In an interview with CNN, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said, “The concept of classical herd immunity may not apply to Covid-19.”
And it “means we won’t be without SARS-CoV-2 in the population for a long time,” according to Fauci, who recently co-authored a report in the Journal of Infectious Diseases on herd immunity.
How did we get rid of the measles?
Measles is an excellent case study in herd immunity, according to Fauci.
The measles virus, like the virus that causes Covid-19, travels through the air. According to the CDC, it is so contagious that if one person has it, 9 out of 10 people in their immediate vicinity will contract it if they are not immune. The Omicron viruses, according to some experts, are as contagious as the measles.
Because of three factors, the United States has successfully eliminated measles transmission and has successfully kept the virus from circulating in the country: an extremely effective vaccine; a virus that does not change or mutate in significant ways over time; and a successful childhood vaccination campaign.
According to the CDC, the measles vaccine is 97 percent effective in preventing the disease. Studies have shown that once a person is vaccinated, they are protected for the rest of their lives.
Many states in the United States had once set a lofty goal of vaccinating more than 90% of their children against the disease by the time they entered kindergarten.
This high level of vaccination coverage, the persistence and efficiency of the vaccine, and the relative stability of the virus have enabled the United States prevent large outbreaks of the illness for more than 20 years.
Herd immunity, however, must extend beyond the United States’ borders. Each year, a certain number of instances develop when tourists bring it into the nation, but it has never recovered a footing here and continued to disseminate, since we have community-level protection against it.
Virus eradication isn’t always successful. In the United States, herd immunity against measles is running down in many regions of the US — and indeed over the world — because of vaccination reluctance.
The World Health Organization warned in 2019 that measles might become prevalent again throughout the world as more individuals decline their immunizations.
Corralling Covid \sCovid-19, however, isn’t playing by those same rules.
“The bad news is that the coronavirus that causes Covid-19 evolves a lot and in substantial ways,” Fauci added.
“We’ve already had five different variations over the course of two years: Alpha, Beta, Delta, and Omicron. Then there’s BA.2 from Omicron “he stated
“Bad news number two is that safe and effective vaccinations are not widely accepted,” Fauci stated. Simply said, not enough individuals have been immunise.
According to Dr. Adam Kucharski, co-director of the London School of Hygiene and Tropical Medicine’s Center for Epidemic Preparedness and Response, the more infectious a virus is, the more individuals must be vaccinated to prevent it from sweeping across a community. Kucharski addressed how expectations around herd immunity must adjust as diseases grow more common in a July 2021 Twitter discussion and a recent interview with CNN.
If the vaccinations now available could prevent 85 percent of viral transmission, Kucharski predicted that 98 percent of the population would need to be immunised for a virus as infectious as the Delta strain.
He believes that if vaccinations didn’t block transmission to that amount, herd immunity would be impossible to achieve with the present vaccines.
Kucharski and his co-authors explain in an article published in the journal Eurosurveillance in May 2021 that a large part of herd immunity is dependent on how successfully vaccinations inhibit transmission — the process of a sick individual transferring the virus to someone else.
Sterilizing immunity is thought to be conferred by vaccines that impede transmission. The measles vaccination gives you sterile immunity. The Covid-19 vaccinations, on the other hand, do not. While immunisation lessens the risk of passing Covid-19 to others, contact tracing investigations have revealed that it still happens.
We may not be able to achieve herd immunity for Covid-19 until most people have developed immunity after getting the infection if not enough people get vaccinated — which has to be virtually the entire population for highly contagious variants — or if the vaccines we have don’t stop nearly all transmission, Kucharski wrote in the article.
There are many additional elements to consider, such as the longevity of immunity over time.
“Not only is vaccine-induced immunity not permanent, but infection-induced immunity is not forever,” Fauci explained, implying that we’ll need to be exposed to vaccinations or infections on a regular basis to keep our defences up to date.
Keeping my fingers crossed
However, some people aren’t ready to entirely abandon the notion.
Barry Bloom is a Harvard University emeritus professor of public health. Making better vaccinations, he believes, is one way to get there.
Companies are developing vaccinations that would target the virus’s more stable parts, such as the spike protein’s stem, which does not appear to evolve as often. This might lead to stronger long-lasting immunity that can withstand the virus’s shape-shifting variations.
Nasal spray vaccinations are also promising, as they may aid in the development of antibodies in the nose and throat. It is hoped that these vaccinations would induce immunity in the tissues where it is most needed, resulting in the type of sterilising immunity that precludes transmission.
If not a vaccine in a nasal spray, why not monoclonal antibodies in a spray that could be used daily before leaving the house to prevent virus transmission, according to Bloom?
“And the concern is, will they be able to eradicate it [the virus] before it spreads asymptomatically? Is this going to be a never-ending game for us to deal with?” Bloom stated in a CNN interview.
Or, as Bloom suggests, perhaps the most we can hope for is evolution’s help. He claims that the virus is evolving to become more contagious over time, but that this does not necessarily mean that it will cause more serious illness. In the end, murdering a person does little to help the virus. It requires hosts. It would be preferable if the virus evolved to be as contagious as possible, but with a lower proclivity for causing severe disease.
Bloom believes that this is what happened to the coronaviruses that cause common colds today. He believes they began as ferocious predators before evolving into pests over time.
That way, not only do they have a chance to live, but so do we.
