a recent New Yorker article reminded me of how interesting I find the concept of herd immunity: the more people in a community who are vaccinated, the lower the chances that our most susceptible members get exposed to an infectious disease. this is especially important for pathogens against which we can’t perfectly vaccinate and for those easily transmissible from person to person. the lower the efficacy and the higher the R0 (number of people secondarily affected by each infected person), the higher the threshold it would take to achieve herd immunity.
friends (very smart friends) often argue with me about their refusal to get vaccinated against the flu. and what i tell them — like i tell conservatives — is, it’s not all about you. some people can’t get the flu shot (because of allergies or other immune disorder, let alone lack of access) and those people are at highest risk of sickness from the flu — often ending in death, not chicken noodle soup. i read that it would have taken 30-40% vaccine coverage to stem the 2008-09 flu epidemic. seems doable! let’s get collective, y’all!