Everything you need to know about “Herd Immunity”

Throughout the Covid pandemic we’ve heard the phrase “herd immunity”. So what exactly is it? It’s appearing not to be as simple a definition as we thought. Scientists are learning things they never knew during Covid and they are re-thinking what it may actually mean.

When most of a population is immune to an infectious disease, this provides indirect protection—or herd immunity (also called herd protection)—to those who are not immune to the disease. For example, if 80% of a population is immune to a virus, four out of every five people who encounter someone with the disease won’t get sick (and won’t spread the disease any further). In this way, the spread of infectious diseases is kept under control. Depending how contagious an infection is, usually 70% to 90% of a population needs immunity to achieve herd immunity……..or so we thought, but I’ll come back to that.

So how can herd immunity occur? Usually a combination of two things. Natural immunity for those who’ve HAD the actual disease or by building up anti-bodies following a VACCINE. The old beliefs around herd immunity would suggest that around 70% of the world’s population would have to actually GET Covid. In the U.S. that would be around 200 MILLION people. As of today we are at 5.4 million KNOWN cases and 170,000 deaths. At a 1% mortality rate concievably we could have 3.3 MILLION death. Let’s hope the new thinking on herd immunity might be right!!

Similarly you would need about 70% of a population to “successfully” acquire immunity through vaccination. It appears that good progress is being made on vaccines and they are currently already in phase III (human trials) here in the U.S. on about 30,000 people. We should know pretty quickly how that goes IF they give us some data on how those trial patients anti-body levels develop. In Russia they are also administering a large number of vaccines to military and hopefully will share valid data. Concerns are that an insufficient number of Americans will actually TAKE a vaccine. So many are filled with doubt about vaccine safety because of the CONSISTENTLY MIXED messages they’ve gotten over the last 6 months……aside from all the FaceBook experts!!

Recently scientists have been gathering some VERY interesting NEW information about herd immunity than they had before Covid. The behavior of the virus is actually pretty strange. Why have infection rates remained so low in NY/NJ and flared in places like Hawaii. Behavior alone doesn’t account for it. THIS from an article I’ll link to below:

“The mainstream narrative is that it’s all about good behavior when cases go down — mask wearing and giving up our social lives for the greater good. And conversely, bad behavior must be what makes them go up. We talk about certain regions having the virus “under control,” as if falling cases are purely a matter of will-power. A sort of moral reasoning is filling in for evidence.” Apparently mask use and bar closings aren’t the only thing accounting for drops in cases.

A few scientists are examining the possibility that previously hard-hit areas are now being affected by a buildup of immunity. This is from another article looking at the “heterogeneity” of populations (diversity in character and content). “This shift is because transmission and immunity are concentrated among the most active members of a population, who are often younger and less vulnerable. If nonpharmaceutical interventions are very strict, no herd immunity is achieved, and infections will then resurge if they are eased too quickly.”

We are also “diverse” in our biology. A recent paper in Science suggests that many people who’ve never been infected with SARS-CoV-2 carry a kind of immune cell, called a T-cell, which recognizes this novel virus and may partially mitigate an infection. These cells may be left over from infections with related viruses — the coronaviruses that cause the common cold! I would surmise that younger more active people are CONSTANTLY being exposed to low levels of viruses and DO develop better immunity overall! Remember the old saying ” a child should eat a pound of dirt before their first birthday”? https://science.sciencemag.org/content/early/2020/08/04/science.abd3871

Statistics professor Gabriela Gomes of the University of Strathclyde in Scotland puts it this way: “What we see is that infections do not occur at random, but that people who are most susceptible to infection get exposed first,” she says, leaving a pool of ever-less susceptible people behind. Her predictions of the spread in the U.K., Belgium, Spain and Portugal have aligned well with reality. Her models keep predicting declines after the infection reached between 10% and 35% of the population. That doesn’t mean the virus has gone away — only that by her models, it won’t explode in those same places again…..like NYC.

So what does this mean for all of us? Society likes to be moralistic when it addresses human behavior. Florida has for some become the Axis-of Evil where Covid is concerned. Numbers here persist at around 5000 new cases per day and about 2% mortality. People here DEFINITELY are heterogeneous and behaviors vary wildly! Young people are going about their lives and those older and possibly at risk are being careful. I do not personally know of ONE of my close group of friends that have HAD Covid although getting tested is STILL a challenge and may take up most of your day and then a 5-7 day wait….RIDICULOUS. Let’s hope that these lower numbers for herd immunity are valid. It would be VERY GOOD NEWS for all of us! I’ll keep you updated on the vaccine and my opinion of it’s safety and effectiveness as data becomes available. Keep an open mind!