Actually it has been expected for quite some time that there should be a gigantic measles epidemic:
>"The second scenario represents the impact of a vaccination programme that reaches high levels of coverage (85% of all new-borns) which are, nevertheless, not high enough to lead to eradication of the agent. However, for the first 15 years after the introduction of vaccination, it appears as if eradication has been achieved, there are no infections. Then, suddenly, a new epidemic appears as if from nowhere. This is an illustration of a phenomenon known as the ‘honeymoon period’. This is the period of very low incidence that immediately follows the introduction of a non-eradicating mass vaccination policy. This happens because susceptible individuals accumulate much more slowly in a vaccinated community. Such patterns were predicted using mathematical models in the 1980s6 and have since been observed in communities in Asia, Africa and South America7. Honeymoon periods are only predicted to occur when the newly introduced vaccination programme has coverage close to the eradication threshold." http://www.ncbi.nlm.nih.gov/pubmed/12176860
The reason is that they underestimated the infectiousness of measles (via airborne routes) when first implementing the vaccination policy. Vaccine effectiveness is not high enough to eradicate the virus, thus we should see a honeymoon period followed by a very large epidemic:
>"The Center for Disease Control (CDC) led in mounting the program with a formal paper at the American Public Health Association annual meeting in Miami in the fall of 1966. Two colleagues and I wrote the “official statement” which outlined in detail unqualified statements about the epidemiology of measles and made an unqualified prediction. My third position in the authorship of this paper did not adequately reflect my contribution to the work.14 I will make but two quotes: 1. “The infection spreads by direct contact from person to person, and by the airborne route among susceptibles congregated in enclosed spaces.” (Obviously the ideas of Perkins and Wells had penetrated my consciousness but not sufficiently to influence my judgment). 2. “Effective use of (measles) vaccines during the coming winter and spring should insure the eradication of measles from the United States in 1967.” Such was my faith in the broad acceptance of the vaccine by the public and the health professions and in the infallibility of herd immunity.
The results of this prediction are well known. The reported incidence of the disease dropped from a level of 400,000-500,000 cases a year during 1960-1964, to 250,000 in 1965 and 200,000 in 1966. This clearly reflected the use of the early-type vaccines in private practice. Incidence further dropped to 50,000 in 1967 and to 25,000 in 1968 but since then has continued a fluctuating cou~s e .T’~he variability can be related to the degree of the total national effort, and the availability of federal funds to defray vaccine costs. Eradication remains elusive although intensification of effort during the past 12 months appears to have brought incidence to a lower point, near 12,000 cases.
There are many reasons and explanations for this rather egregious blunder in prediction. The simple truth is that the prediction was based on confidence in the Reed-Frost epidemic theory, in the applicability of herd immunity on a general basis, and that measles cases were uniformly infectious. I am sure I extended the teachings of my preceptors beyond the limits that they had intended during my student days.
In the relentless light of the well-focussed retrospectiscope, the real failure was our neglect of conducting continuous and sufficiently sophisticated epidemiological field studies of measles. We accepted the doctrines imbued into us as students wikout maintaining the eternal skepticism of the true scientist." https://www.ncbi.nlm.nih.gov/pubmed/6939399