A global pandemic is as complicated a natural phenomenon as there is. And trying to sort through the data (much of which is crap) during the pandemic is fog-of-war stuff at its densest. But I believe it is becoming clearer that we are likely going to be in a period between now and when a vaccine is released where two factors – the relaxation of suppression and growing natural immunity – will be pushing the numbers in opposite directions. The course of the pandemic will be determined by which proves to be the strongest.
Across the world, countries have adopted various suppression tactics (lockdowns, masks, banning large gatherings, etc. technically referred as non-pharmacological interventions) in an attempt to slow the spread of the virus. In the early days of the pandemic this was referred as “flattening the curve.” The original idea behind this concept was to spread the outbreak out over a longer period of time to keep from overwhelming the healthcare system. However, somewhere along the way, suppression tactics went from being a temporary brake on the virus’s spread to an ultimate solution. They were going to “crush” the virus.
Suppression can protect discreet populations (island, nursing home populations, etc.) until an epidemic passes, but it is not an effective technique for ending an epidemic in a large population. That only occurs when a sufficient portion of a given population becomes immune to the disease, either naturally or through a vaccine. (See Notes 1 & 2.)
The history of previous epidemics demonstrates that suppression tactics are difficult to implement and even more difficult to sustain over extended periods. Generally, suppression tactics exact high costs both economically, as we have so dramatically seen, and in the unanticipated consequences, like the recent surge in suicides. Even relatively benign measures, like masks, go fundamentally against our ingrained natures. If you lean over a baby with a mask on, most will instinctively try to lower it. So, suppression tactics should always be regarded as temporary measures to minimize the amount of serious illness and fatalities while getting to herd immunity.
The concept of herd immunity has, as with so many other issues regarding COVID, become highly politicized, especially after President Trump appointed Scott Atlas to his COVID task force. Atlas is a Stanford professor who has been more optimistic about the prospects for herd immunity. In the wake of this appointment to the task force, there were dozens of media stories attempting to debunk the concept of herd immunity. Many repeated the early indications that herd immunity would not be attained until 70-80% of the population had been infected. But those early estimates have been almost universally abandoned by epidemiologists in favor of significantly lower levels. Widely regarded Harvard epidemiologist Marc Lipsitch was quoted this week by the Atlantic estimating herd immunity at 20-60%. Back in the spring anyone suggesting that herd immunity might be attained at 20% would have been laughed out of the room.
But thinking of herd immunity as a threshold is a mistake regardless. Naturally acquired immunity begins when the first person is infected and recovers. That takes that person out of the “target pool” for the virus’s subsequent attempts to spread. Every person who becomes immune makes the ability of virus to spread incrementally harder. It is, in effect, a natural brake on the spread of the virus much in the same way that suppression tactics are.
Of course, the end game is a vaccine. When one will be available and how quickly it can be distributed are still open questions. But between now and whenever that is, the course of the pandemic will most likely be determined by the conflicting forces of the relaxation of suppression tactics and the growth of naturally acquired immunity.
My guess is that it will be, more or less, a standoff. If the rate of spread continues to fall, or even stays at the current level, there will be little support for suppression tactics and compliance with them will wane. If there is an increase in infections, there may be little appetite for the more extreme measures such as lockdowns, but people will modify their behavior and become more cautious. So, the relaxation of suppression will likely move sympathetically with the growth of naturally acquired immunity.
If that is right, the level of serious disease will likely remain about the same until a vaccine is rolled out, ebbing and flowing around specific events like school reopenings. But looking at the trend over the last two months and considering the history of previous epidemic’s curves, it is hard to imagine a major spike in serious disease in the intervening months before a vaccine is rolled out. However, we have seen how quickly this virus can spread if it finds the right conditions.
So, for now we keep our guard up and hope that our immune systems are doing their job as quickly as possible.
Note 1: There are some diseases that have peculiar transmission mechanisms or are so highly lethal that they have been contained by suppression. For example, Ebola, which spread by contact with human fluids, was brought into check largely by getting villagers to discontinue certain cultural practices that spread the virus (e.g., bathing with corpses). Similarly, SARS-CoV-1 and MERS were both very lethal, which is detrimental the virus’s ability to spread. But outside such instances, epidemics end when herd immunity is reached.
Note 2: I do not have space to address the “immunity deniers,” who postulate that humans may not become immune to COVID. I will just say that it is complete and utter nonsense. There is zero “science” to support such a proposition. I have not seen a single epidemiologist suggest that there will be no immune response and, of course, Dr. Fauci famously said, “I will bet anything that people who recover are really protected against reinfection.” Also, this article in Forbes has a good discussion of the issue. Frankly, the best evidence that the human immune system will produce natural immunity is that you are here to read this post, because if not, the human race would have been long ago wiped out by some rogue pathogen. The defense may not be a complete or perfect immunity, and there may be a small number of people that will be reinfected. But it will be, at least, sufficient to drive COVID into a background disease.