Sunday, October 4, 2020

Herd Mentality

                                                                                         written 27 September 2020

                                                                                           published 4 October 2020


            President Trump recently mentioned that the new federal Covid-19 goal is to create "herd mentality".  This engenders images of lemmings mindlessly following the leader over the cliff, or panicky stampeding buffalo.  Trump was trying to describe herd immunity, but we know about Freudian slips.

            Last month, Trump installed a new advisor for Covid-19, Dr. Scott Atlas, a radiologist with no epidemiological experience, but a frequent talking head on Fox News.  Atlas advocates creating herd immunity as soon as possible, which appeals to Trump as it requires little federal action.

            With most diseases, an infection survivor builds antibodies which can protect against future re-infection.  When a significant portion of the society (50%-90% depending on infectiousness) has this antibody protection, large-scale infections disappear.  This is called herd immunity.  In some diseases, the protection lasts a lifetime, in others it fades with time, sometimes within months.  If the disease mutates sufficiently, previous antibody protection may no longer work, which is why a person can get the flu again the following year.

            Covid-19 is a new virus, so critical information is still emerging.  There are reports of people being re-infected, and data showing antibodies rapidly decline after a few months, raising questions about developing herd immunity through wide- spread infection.  Putting aside the question of the possibility of herd immunity, we can examine the human cost of deliberately pursuing this approach.

            On September 27th, listed 7.3 million cases (2% of the US) and 209 thousand deaths, giving a death rate of 2.8%.  If we allow that another 7.3 million folks might have been infected (a total of 4%), but recovered without being tested or presenting at a hospital, we get a death rate of 1.4%.  If we take a 70% target for herd immunity, we need to infect another 232 million Americans, of whom more than 3 million will die at current rates. 

            But that is a serious underestimation of the deaths that will result.  About 15% of those infected require some hospitalization, and a fifth of those require ICU care.  At that rate, of the 232 million new infections required to hit herd immunity, 35 million will need some hospital care, of which 7 million will need ICU care.  However, the US has about 930,000 hospital beds and 100,000 ICU beds.  An out-of-control infection would overwhelm the entire hospital system.  Many people who would survive Covid-19 with the proper care will die and all the "normal" health issues will become more lethal as well.  In June, when the US case load was four times smaller, over 600 nurses and doctors on the front line had already died.  With another 232 million infections, those numbers could approach 20,000: each death decreasing the efficiency of the health system.

            But even that isn't the whole story, because it focuses just on deaths.  Those who survive Covid-19 are also affected.  Over 30% have inflamed heart muscles, and 10% have blood clots.  Long-term effects, such as gastrointestinal disorders, extreme fatigue, erratic heartbeat, memory loss, and brain fog, some still unresolved after five months, have been reported in 10% of the infected population, suggesting another 23 million people would be affect before hitting herd immunity.  

            The White House herd immunity plan suggests that we simply isolate the vulnerable and the rest should do fine, with Trump recently claiming 99% are unaffected.  But the 15% of Americans over 65, the 35% of Americans who are obese, the 10% of Americans who are diabetic, and the 4% who are immune-compromised are all vulnerable.  While there is some overlap in these groups, it is hard to imagine how to isolate all these people, especially if we don't test everyone to know who is actually infected.

            Herd immunity has short term political attraction for Trump, but the human and economic costs will be enormous.  In addition, Republicans are trying to repeal the Affordable Care Act and eliminate coverage for pre-existing conditions like Covid-19 damage, which will adversely affect health care for 100 million Americans.  The issue will be heard before the Supreme Court the week after the election, which is part of why Republicans are rushing to install a new Justice.

            This will be the most consequential elections in US history, affecting the health of our people and our democracy.