The earliest notes on the reproduction number in relation to herd immunity: Theophil Lotz and smallpox vaccination

During the late 19th century, the earliest epidemiologic evaluations of vaccination were performed on smallpox, the first disease against which a vaccine was developed (Fenner et al., 1988), and some of the results even raised the hope to eradicate the disease supported by an original theory (Lotz, 1880).