Global Health NOW: The Myth about Herd Immunity
Lavanya Vasudevan, assistant professor of family medicine and community health, and global health at Duke University, and Gavin Yamey, professor of the practice of global health and public policy and director of Duke University’s Center for Policy Impact in Global Health

“…Disturbingly, vaccine refusals are increasingly the reality in many parts of the U.S. and elsewhere. … [T]hese trends signal a dangerous lack of public understanding about how herd immunity works. Typically, 93% to 95% of a population must be vaccinated to achieve herd immunity and prevent an outbreak of measles. … But even … with rates above 93%, herd immunity offers no guarantees. The protective effect of herd immunity can vary based on the ‘herd’ that an individual moves with. Relocation, travel, or even a new circle of friends can change the composition of one’s herd, and thus its shared protection against infection. … And there’s another reason to worry about potential measles outbreaks: New findings suggest that when children are infected with measles, the virus wipes out the protective effects of previous vaccinations against other diseases. … While vaccinations are often framed as an individual decision, these impacts on public health should not be undersold. Doctors and public health officials need to be more proactive in explaining these benefits…” (12/11).