In the 1986 edition (no. 11) of the British National Formulary - which is jointly produced by the British Medical Association and the Pharmaceutical Society of Great Britain - on page 390 under the heading of "mumps" in the section of vaccines, we read:

Since mumps and its complications are very rarely serious there is little indication for the routine use of mumps vaccine.

So in 1986 the British Medical Association and the Pharmaceutical Society stated that both mumps and its complications are very rarely serious - what then suddenly made this very mild childhood disease into a "killer disease" which necessitated scaring the wits out of parents in the few years to follow? It's a question that needs to be answered.

Anywhere, here is the proof for the above quotation:

And the cover for this edition: