That doesn't mean they had adequate production capabilities. It may have taken time to get production up to an efficient level.

Two other factors to consider: when was cryogenic storage of vaccines/mRNA first done successfully, and when were mRNA gene therapies first developed? Assuming any of this holds water, including OP, that could help pinpoint when this might have been developed.

from https://cryogenicsociety.org/resources/cryo_central/history_of_cryogenics/

(emphasis mine)

Medicine Cryoprotectants, 1946 and 1959, UK The discovery of cryoprotectants, such as glycerol, in 1946, by Polge and Smith, and dimethylsulfoxide (DMSO) in 1959 by Lovelock and Bishop, for ensuring the survival of cryopreserved cells and tissues, provided the breakthrough for the development of the cryopreservation of spermatazoa, embryos, ovaries, blood and other tissues, which is taken for granted today.

DMSO has some interesting properties, one of which is why its use in humans is banned in the U.S.(although coincidentally, you can get it for horses), namely that anything dissolved in it will be carried by it through the skin. This is great if you're, say, trying to give someone a vaccine or a supplement without injecting them, not so great if you forget to swab their arm thoroughly first; any toxic substances on the skin will be pulled into the body along with the dmso, which is why it's so important that you wash whatever area of the skin you want to apply it to thoroughly before doing so.

Edit: I'm not sure why, but this seemed relevant somehow...