Goal: Herd Immunity

"Our findings highlight that vaccination does not only protect the individual who receives it, but is likely to reduce viral shedding and therefore transmission to the population."

Israeli Analysis

(Kenneth Ferriera/Lincoln Journal Star via AP)

"Herd immunity can also be reached when a sufficient number of people in the population have recovered from a disease and have developed antibodies against future infection. For example, those who survived the 1918 flu (influenza) pandemic were later immune to infection with the H1N1 flu, a subtype of influenza A. During the 2009-10 flu season, H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu.

"However, there are some major problems with relying on community infection to create herd immunity to the virus that causes COVID-19. First, it isn't yet clear if infection with the COVID-19 virus makes a person immune to future infection.

"Research suggests that after infection with some coronaviruses, reinfection with the same virus — though usually mild and only happening in a fraction of people — is possible after a period of months or years. Further research is needed to determine the protective effect of antibodies to the virus in those who have been infected.

"Even if infection with the COVID-19 virus creates long-lasting immunity, a large number of people would have to become infected to reach the herd immunity threshold. Experts estimate that in the U.S., 70% of the population — more than 200 million people — would have to recover from COVID-19 to halt the epidemic. If many people become sick with COVID-19 at once, the health care system could quickly become overwhelmed. This amount of infection could also lead to serious complications and millions of deaths, especially among older people and those who have chronic conditions."

Mayo Clinic

"Surrendering to the virus [by allowing it to run through a community unchecked to infect the population to achieve herd immunity is not a defensible plan]." 

"[Such an approach would lead to a catastrophic loss of human lives without necessarily speeding up society’s return to normal]. We have never successfully been able to do it before, and it will lead to unacceptable and unnecessary untold human death and suffering."

Kristian Andersen, immunologist, Scripps Research Institute, La Jolla, California

ICU health-care worker Jannikka Navaratnam cares for a patient inside a negative pressure room at the Humber River Hospital during the COVID-19 pandemic in Toronto. (Nathan Denette/The Canadian Press)

 

Infectious diseases are difficult to eradicate, and it has been this way throughout human history where one type of virus after another has run amok through human populations, devastating communities whenever a new  virus emerges. Hundreds of years ago during the colonial era, European colonial powers brought new pathogens with them when they invaded and colonized populations on other continents, in some instances seeing 90 percent of the population that had never before encountered such viruses wiped out; it happened in Peru when the Spanish conquistadors arrived.

 

In our current, modern era, science enables human populations to rely on research to produce vaccines so that mass inoculation will either (rarely) eradicate a virus entirely or succeed in keeping it under control. From measles to polio to mumps these deadly diseases still can lethally infect, but vaccines have them under control. Once a certain proportion of a population becomes immune to a disease, the herd effect takes over, protecting those members of that population that for one reason or another cannot be vaccinated.

Herd immunity thresholds differ with each disease; measles as an example is so infectious that a 90 percent vaccination rate is required to dampen its enthusiasm in attacking a vulnerable population. Mumps is able to be contained at a 75 percent herd immunity. COVID-19 was initially and erroneously estimated to be not very contagious so that estimates as low as ten percent to achieve herd immunity were theorized. Medical science has since learned quite a bit more about the SARS-CoV-2 virus causing COVID.

The assumption now among public health agencies was that the figure of 66 percent herd immunity may be the magic number to be achieved. Until a study from the Brazilian city of Manaus showed upward of 76 percent of the population had contracted and survived COVID-19, easily surpassing that 66 estimate. Israel's first-place status in inoculating the largest proportion of its population of any other country in the world has the attention of the medical world fixated on its progress. Given restrictions on vaccinating children set aside, the Israeli experience may give a fixed fugyre to the number of vaccinations to be achieved to see hospitalization and death go into free-fall.

 

COVID-19 lockdowns have overwhelmingly impacted the world economy, its production, its employment, its health care systems, its patience. There were proposals to allow the disease to run its course while protecting vulnerable populations, which was what Sweden chose to do. It managed to preserve its economy to an extent its neighbours who instituted full lockdowns were unable to achieve, but in the end, the country experienced a death rate found to be ten times greater than its neighbours.

 

New York City's experience in the spring of 2020 was quite different, when it became the worst-hit epicentre in the world. It was thought that the catastrophe in the spring at the very least rendered the city resistant to any future outbreaks. However, when a second wave swept through the city it turned out to be a repeat of the first. Since then studies discovered that up to 90percent of New Yorkers may yet be susceptible to infection by COVID-19.

 

Should countries decide to pursue a strategy of "natural herd immunity", a team of researchers warned in a widely circulated letter published in The Lancet, the result could well be that thousands of unnecessary deaths would occur; no notable gains in resilience would result. The frantic rush by scientists with pharmaceutical companies to succeed in designing a successful vaccine led to a formula to stop people from experiencing the worst impacts of COVID infection. On the other hand, it remains unknown whether those same people could still 'shed' the virus and infect others. 

 

Also unknown is how long the vaccine effects might last; whether it could confer (unlikely) lifetime immunity, last for years, or have to be re-administered annually with a new formulation like the seasonal flu. Science does have a hint of an answer to that critical question, in that people who have recovered naturally from having been infected have been re-infected with COVID. There is much yet to be known about COVID-19, including the potential rate of reinfection, particularly post-vaccination.

 

And then too, there is the reality that the current vaccines now in circulation have efficacy rates from 70 percent to 95 percent. Which leaves 30 and 5 percent respectively of people for whom vaccination does nothing to avert either contracting the pathogen or experiencing milder reactions from its onset. And non-symptomatic cases famously go on to infect others in an endless cycle ... until such time as all the pieces of the puzzle fall into place ... if ever.

 

In a troubling sign, COVID-19 is already reinfecting people who have recovered naturally from the disease. Photo by Ryan Remiorz/The Canadian Press