Complex sentence: The view of the British government throughout was that vaccination was safer than variolation, and this is not generally disputed; variolation was safer than random infection with smallpox, but potentially spread smallpox infection itself.
Split into simpler sentences: The view of the British government throughout was that vaccination was safer than variolation, and this is not generally disputed. Variolation had been shown to be safer than random infection with smallpox, but potentially spread smallpox infection itself.