Is Herd Immunity the Answer to Defeating COVID-19?

March 16, 2020 – When I was very young I got chickenpox, not once, not twice, but three times. The first time I picked it up from one of my brothers. The second and third time I got it from being in the community. I presented no immunity to varicella voster and still have none. I have had a shingles shot to stop, hopefully, the reemergence of the virus in my system in my 70s. I will have the new shingles shot shortly, but not until I have had knee-replacement surgery this year.

When you think of herd immunity, chickenpox comes to mind because I remember parents having chicken pox parties to expose their children to someone who was infected so they would develop lifetime immunity to the disease. Unbeknown to most parents, chickenpox presents as a rash but is in fact a respiratory disease. For children with underlying respiratory and heart problems, getting it can be deadly. When my daughter who was born with congenital heart disease was finally able to go to school, anytime a chickenpox outbreak occurred she was home-schooled until it had finished its course through the children in her class. Her heart-lung condition left her extremely vulnerable to this childhood disease seen by many as largely a benign nuisance.

So what’s involved when the Prime Minister of Great Britain, Boris Johnson, proposed to tackle COVID-19 using a herd immunity strategy this week?

Herd immunity relies on exposing a relatively healthy group to a disease to accelerate the development of immunity within a total population. It is method that doesn’t require the development of a vaccine. And it is in direct contrast to the isolation strategy currently being implemented here in Canada, in Italy, Spain, France, and China.

If you create a viral load in the larger community that is sufficient, then those who survive the disease become immune. Once enough of the general population has been exposed and acquired immunity, then those most vulnerable are less at risk.

In Great Britain, with a population of 66.4 million, for a herd immunity strategy to work, up to 80% of the population would have to be exposed or infected by COVID-19. How could the system cope with that many infected? How many of those would require hospitalization? How many would die before herd immunity gets established?

As of yesterday, Great Britain had 1,143 COVID-19 cases and 21 deaths. That’s a 1.8% fatality rate. The current rate of fatality for the virus is 3.4% according to the World Health Organization. If up to 80% of the British people were exposed to the virus, how many in theory could die? At 3.4% the number would be 2.25 million deaths. Chinese studies based on the outbreak there put the mortality number lower, 2.8% for infected men, and 1.7% for women. Blending those two gives us 2.25% which would mean almost 1.5 million deaths. And if the current fatality rate were to be maintained at 1.8%, it would mean almost 1.2 million.

As one writer stated yesterday in commenting on Johnson’s notion of herd immunity, that’s “shoving one hell of a lot of people of a cliff.”

So it should be no surprise to you, my readers, that since the Prime Minister proposed his herd immunity solution, the pushback has been severe. Herd immunity is off the table, the musings of a fevered mind that has the same tendencies as the leader of the United States, in commenting before thinking about the implications.

Where are we with COVID-19 as I write?

As of March 16, 2020, 2:34 Eastern Daylight Savings Time:

Cases: 179,829 with 94,463 active, ranging from 93% mild symptoms to 7% serious or critical. China remains the original epicenter but new cases have dramatically declined as have deaths. Europe, the new epicenter has close to 62,000 infections. Canada has 376 currently while the United States’ numbers have climbed to 4,180.

Deaths: 7,074 (3.9% of the total number of cases to date).

Recovered: 78,292 (43.5% of the total number of cases to date).