COVID herd immunity: At hand or forever elusive?

By MICHEL ACCAD, MD With cases of COVID-19 either disappeared or rapidly diminishing from places like Wuhan, Italy, New York, and Sweden, many voices are speculating that herd immunity may have been reached in those areas and that it may be at hand in the remaining parts of the world that are still struggling with the pandemic.  Lockdowns should end—or may not have been needed to begin with, they conclude. Adding plausibility to their speculation is the discovery of biological evidence suggesting that prior exposure to other coronaviruses may confer some degree of immunity against SARS-CoV2, an immunity not apparent on the basis of antibody seroprevalence studies. Opposing those viewpoints are those who dismiss the recent immunological claims and insist that rates of infections are far below those expected to confer immunity on a community. They believe that the main reason for the declining numbers are the behavioral changes that have occurred either under force of government edict or, in the case of Sweden, more voluntarily. What’s more, they remind us that the Spanish flu pandemic of 1918-1919 occurred in 3 distinct waves. In the summer of 1918 influenza seemed overcome until a second wave hit in the fall. Herd immunity could not possibly have accounted for the end of the first wave. The alarmists may have a point.  However, recent history offers a more instructive example. Until early 2015, epidemiologists considered...
Source: The Health Care Blog - Category: Consumer Health News Authors: Tags: COVID-19 Health Policy immunity MICHEL ACCAD Pandemic Source Type: blogs