Sort of
Yes, 4,000 iU isn't enough and will be used for higher priority purposes but also you have to remember that this 4,000 isn't addressing the chronic vitamin D deficiency that had probably been going on for years.

So 4,000 IU is not only not enough to maintain a healthy status but it is definitely not enough to "fill the hole" and help correct years recurring and or ongoing deficiency.

Also, remember MS vulnerability can start in the womb and that condition can be mitigated but not cured post delivery.