4:22 p.m. - 2021-01-18
HERD IMMUNITY MENTALITY
Problems:
1. How many people have to be infected with Coronavirus in order to achieve herd immunity? (Estimates range, but most epidemiologists think between 60 and 70%. Current US population is 331 million. 60% of that is 197 million.)
2. How many of the above would die? (Michigan death rate is 4%. If that held true, then 7.9 million would die in US.) The New York Times estimates 1.6 deaths per 100 infected. That would mean 3 million deaths in the US.
3. How many would suffer long term consequences, either medical or financial? Reports of so-called "long haul" patients include alarming and persistent symptoms for weeks after the patient has "recovered" from Covid.
4. Would the healthcare system be overwhelmed? Remember that in the pursuit of herd immunity, many of those infected would be healthcare workers, taking them off line for an indefinite period--those that survived.
5. If #4 happens, what would be the effect on patients with other medical conditions? How would hospitals triage? Would they be forced to move from triage to rationing health care?
6. How would we pay for the treatment of a large number of infected individuals? (Including the impact of ending Obamacare, currently before SCOTUS.) What would be the impact on the workforce?
7. How would we protect the more vulnerable members of the population?
8. Does one infection with this virus elicit immunity to subsequent exposures? There have been reports of second infections; how prevalent this phenomenon may be is not yet known. Other coronaviruses are capable of reinfecting previously recovered individuals.
9. Would we stop wearing masks? End social distancing? If so, how would vulnerable people interact with the rest of society? Is it ethical to pursue a "strategy" that forces vulnerable people to continue self-isolating while the rest of society opens up?
10. What would be the effect of viral mutation on herd immunity? Mutant strains have been reported in the UK, South Africa, and Nigeria, and are likely to spread just as the original virus did. At present the mutation affects contagion and is not more lethal, but other mutations are possible.

Typically, herd immunity is discussed as a desirable result of wide-scale vaccination programms. High levels of vaccination-induced immunity in the population benefits those who can’t receive or sufficiently respond to a vaccine, such as people with compromised immune systems. Many medical professionals hate the term herd immunity, and prefer to call it “herd protection." That’s because the phenomenon doesn’t actually confer immunity to the virus itself—it only reduces the risk that vulnerable people will come into contact with the pathogen. Public health officials usually don't talk about herd immunity in the absence of a vaccine.

Even when "herd immunity" is achieved, it's still possible to have outbreaks, especially in areas where immunity is low.

Also, the value of R0 changes if measures to control the virus are stopped. If we calculate a percent needed to be infected to reach herd immunity based on current R0, then stop using masks, etc, the R0 would go up, and so would the herd immunity threshold.

The R0 is determined in part by the biology of the virus but also by the behavior of the population. Therefore, calculation of R0 is a moving target. And the herd immunity threshold is not a magic number. When we reach 70%, for example, infections don't automatically stop.

Sweden has been held up as a "success story" for the pursuit of herd immunity, but Sweden's per capita infection and death rates are much higher than those of neighboring Norway.

We know very little about long-term immunity to Covid following an infection. Patients need to be followed over longer time spans. Immunity to cold viruses wanes after about a year. There have been reports of second coronavirus infections, but not enough data to draw conclusions. But if immunity wanes after a year, herd immunity can never be achieved.

If society decides to move toward so-called herd immunity, would it be wise for all of us--including the more vulnerable segments of the population--to conform? There are strong arguments for postponing one's exposure as long as possible. The chance of developing a vaccine is part of that argument, but we should also keep in mind that the medical profession is getting incrementally better at treating Covid. The rejection of hydroxychloroquine, the better use of dexamethasone, availability of antibody preparations, more selective use of ventilators, and even turning patients to a prone position have all had favorable impacts on patient survival. Covid patients today benefit from the medical profession learning from earlier mistakes, and the same is likely to be true for patients who aren't exposed for several more months. 

Performing randomized, controlled trials--the gold standard of scientific medicine--not only takes time; it is also very difficult to do when hospitals are full and doctors are overworked. The pressure to try something--anything-- that might help when beds are full and people are dying is likely to be much greater.

When new drugs and therapies are proven to be effective, there will inevitably be a lag time for manufacture and distribution. According to Sarah Zhang, writing in THE ATLANTIC, "All of this means that COVID-19 treatments are likely to become both more effective and more accessible in the future. And eventually there will be a vaccine. At some point, COVID-19 will become a manageable disease, akin to the flu. There will never be a good time to get the coronavirus, but getting it later will almost certainly be better than getting it today, tomorrow, next week, or even next month."

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