By Dr. Stephen A. Berger

WHAT IS Herd IMMUNITY?

It stands to reason that a contagious disease should disappear from a population when a sufficient percentage of potential victims – “the herd” has become immune. This outcome may arise because a massive number of individuals have been either infected or vaccinated.

Most authorities dealing with COVID-19 have set the goal for herd immunity at >60 percent; however, the precise percentage for any infectious disease will depend on many factors involving demography, virulence, route of infection, etc. 

HAS AN INFECTIOUS DISEASE EVER BEEN ERADICATED BY REACHING HERD IMMUNITY?

Infectious Diseases have been known to reach herd immunity, however, none have been permanently eradicated by it. For instance, although there was an observed decrease of measles infections during the 1930s, recent outbreaks indicate the disease is far from being eliminated – despite effective vaccination measures introduced in 1963.

IMPORTANT CONSIDERATIONS

As many countries enter into a second-wave of this pandemic, the bottom-line question for those who advocate the achievement of herd immunity through mass infection of the population will be one of cost-benefit. 

This prompts a few thoughts and questions. Any program to actively infect large numbers of individuals will begin with the isolation of the elderly and other high-risk populations. How many countries are truly equipped to house, feed, isolate, and treat millions of people in these categories? Do they have the manpower, physical structure, and funding?

It is important to note that the 2002-2004 SARS outbreak was not brought to an end by herd immunity, but rather through stringent public health methods implemented by affected countries. 

HOW MUCH TIME WILL BE REQUIRED TO ACHIEVE HERD IMMUNITY?

My country (Israel) has a population of 8.8 million and is currently experiencing 1,000 to 2,000 new cases per day. If we allow the current disease rate to continue, it will take perhaps three more years (!) to exceed 60 percent immunity. 

Would the Health System – already at capacity – be able to sustain all of this? Is there proof that COVID-19 infection even leads to immunity?  In what percentage of patients? Does immunity persist for more than a year or two?  Will immunity also “cover” newer strains of coronavirus?

Several COVID-19 vaccines will be released for general use in the next three to six months. Assuming that these vaccines are effective, targeted mass-infection at this point will cause more harm than good… and at best be a case of “too little, too late.”

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