BECAUSE PRISON officials rarely win much applause -- and because last year it looked as if a large number of Virginia's inmates had contracts with escape clauses -- a dramatic statewide improvement in the last 12 months deserves note. Escapes dropped to their lowest point in a decade -- down to half the number of inmates who fled during the previous year. While that previous year was not a great one -- and while there is still a continuing problem at Fairfax Correctional Unit 30 -- the change is an encouraging sign for the current administration of the state's department of corrections under Alan R. Sielaff, a former top aide to Gov. Charles S. Robb. Since taking over the department in January, Mr. Sielaff has instituted a number of security measures, and the decrease in escapes during this period is particularly notable.

For the fiscal year that ended June 30, there were 54 escapes, including 27 trustees who walked away from unguarded posts. This compares with 108 in the previous year -- a total that included the May 1984 breakout of six death-row inmates from the Mecklenburg Correctional Center. That set off a massive reorganization of Virginia's corrections system, as well as expenditure of millions of dollars on security and personnel improvements. The escape rate for the fiscal year just ended was 5.2 per 1,000 inmates. In fiscal 1974, the rate was 87.2 per 1,000. And today the number of prisoners is about 10,300 -- nearly double that of fiscal 1974.

Even in a statewide election year, Mr. Sielaff is winning bipartisan support for his handling of the job. He cites a "growth of diligence by all staff" as a big factor in the improved record. While security alone is not a measure of any state's ability to cope with the complexities of correctional policies -- who should be in what kinds of isons, for how long and under what conditions -- it is fundamental to restoring the public's confidence in penal administration. When a serious and alarming defect is addressed effectively, there is better opportunity to deal with the tough remaining issues.