Regular immunization throughout the United States begins…

Regular immunization throughout the United States begins in 1860.

The 8th edition of the Encyclopaedia Brittanica, published in 1860, states "nothing is more likely to prove hurtful to the cause of vaccination and render the public careless of securing to themselves its benefits, than the belief that they would require to submit to re-vaccination every 10 to 15 years". (Some years later, the 11th edition will reverse its position with the statement, "it is desirable that vaccination should be repeated at the age of 7 to 10 years, and thereafter at intervals during life".)