President Thomas Jefferson in 1806 wrote a letter to English physician Edward Jenner. Ten years earlier, Jenner had intentionally infected a boy with cowpox, in order to protect him against the much more terrifying smallpox disease. It worked. Jenner gathered more evidence, and two years later he published his Inquiry into the Variolae vaccinae known…

Vaccines Can’t End Pandemics Alone—And We’ve Known That Since We Eradicated Smallpox