https://researchbriefings.files.parliament.uk/documents/CBP-8556/CBP-8556.pdf&ved=2ahUKEwj2iMT-htqSAxX5S_EDHY-IKkAQFnoECCgQAQ&usg=AOvVaw0ZTV0FwNc5M_GjiKwF5gNM.
The MMR graph in this document shows that we are slightly below the vaccination coverage of the late 1990's after which there was a significant drop, then a rise and recently a slight drop taking us back to slightly below the 1998 level. Based on the data points in this documents, the overall coverage for this entire period is significantly less than the current coverage.
MMR introduced in 1988.. since then, there have been ups and downs in the vaccination rates (we ut the deaths have remained very low, despite these vaccination fluctuations. The data linked above shows adult and child deaths from 2005 (20 years ago) There have been 5 child deaths from measles where there was no severe immunological issue present since 2005 and 4 child deaths where there was an immunological issue.
Pre MMR, 1988, the deaths were in double figures annually, so no, I do not think that coverage since the introduction of the MMR is masking what would otherwise be a higher mortality rate based on current vaccination coverage rates.