Re: Should measles vaccination be compulsory?
I hope to help clarify some facts about this issue. The concept of herd immunity arises from simple ordinary differential equation models that assume random mixing of population at risk. In this model a preschool child in St.Andrews, St Davids or Westward Ho! has the same chance of being in contact with a person with measles arriving in London, as a similar child in say Kensington and Chelsea….
As Keeling and Eames  have shown the contact network structure alters the level of immunisation effectiveness required as well as uptake to establish full protection of the population. Indeed if the network of contact is scale free then only universal coverage with full efficiency will lead to eradication. Thus calculating the protective threshold requires a complete knowledge of every persons contacts, and is likely to be much higher than the figures routinely quoted.
The history of Smallpox immunisation in the UK shows that, though mandatory vaccination was introduced in 1853, endemicity in England and Wales was only abolished in 1934! And in the two years before compulsion was abandoned (1946 & 1947) 14 and 15 deaths respectively were reported.  The authoritative “Red Book” states that the removal of endemicity was due to the UK Authorities reacting “effectively with surveillance, the isolation of cases, and the vaccination of contacts” (page 326).
Indeed, according to WHO, “before 1967, smallpox eradication strategy relied on mass vaccination. However this strategy was ineffective in densely populated regions where containment measures proved more effective.” 
We know that isolation and quarantine of contacts is effective, especially if combined with ring vaccination within a short period. Since the level of immunisation with Smallpox to achieve “Herd immunity” is lower than that theoretically required with measles, it seems to me that attempting to achieve what proved impossible when the population was more obedient and less able to travel is doomed to failure.
Regardless of the method used to raise immunisation rates, experience suggests that compulsion does not achieve universal immunity. However, investing in an active surveillance system, with well-resourced local teams responding to control outbreaks, seems a more likely route to success. It worked before but will take many decades. Meanwhile, all parents should be encouraged to help protect their own children by the full immunisation schedule.
1 Keeling MJ, Eames KTD. Networks and epidemic models. Journal of the Royal Society, Interface 2005;2: 295–307.
2 Fenner F, Henderson DA, Arita I, Jezek Z, Ladnyi ID. Smallpox and its Eradication. Geneva: WHO, 1988. http://whqlibdoc.who.int/smallpox/9241561106.pdf (accessed 10 Jun 2019).
3 WHO. The Smallpox Eradication Programme - SEP (1966-1980), 2010. https://www.who.int/features/2010/smallpox/en/ (accessed 10 Jun 2019).
Competing interests: No competing interests