<p>➀ Vaccines have been used since May 14, 1796, when Edward Jenner first vaccinated against smallpox.</p><p>➁ Diseases like polio and smallpox have been eradicated, with no new cases in the United States for decades, compared to over 10,000 cases per year in the 20th century.</p><p>➂ Progress in eradicating measles has slowed in recent years but remains significantly lower than the 20th century average of half a million cases per year.</p>