Why aren’t covid-19 vaccines being manufactured in standard prefilled syringes?

Prefilled syringes are the safest and standard recommended delivery device for most modern vaccines—so why are covid-19 vaccines being packaged in glass vials in the middle of a global glass shortage?

Here is a short tutorial about pharma vials and syringes.
I was responsible for container/closures for pharma products for over 38 years, Abbott, Hospira and Amgen...

Glass for pharmaceutical products is almost always “Type I”, borosilicate glass. This formulation includes boron and other additives to the silica which make the resulting container quite resistant to the contents.
Other types of glass for containers is referred to as “soda-lime glass is is more suitable for aqueous formulas with stable pH and low concentrations of active ingredients.

The sand used in Type I glass must be clean and pure. “Beach sand” is usually just broken up shells of calcium carbonate which, of course, is not silica dioxide.

So, now we have a container to put the vaccine into.
The next parameter to satisfy is CLOSING the container.
Unless you are using glass ampules which are closed with fire melting the tip shut, you need something resiliant to seal the vials and syringes.

Synthetic rubber compounds have existed for 30 years that do not contain any natural dry rubber. These halobutyl compounds fit the bill quite well. The stoppers are made in USA EU and Japan for the most part by West, Daikyo, Datwiler and others in the proper sizes to fit vials and syringes.

Vials also require an aluminum closure to keep the stopper in place and under compression to assure no microbial contamination can occur during shipping and storage. ALL pharma packaging for ALL therapeutics MUST pass “container/closure integrity (CCI) testing to prove that under ALL condition, the stopper and container to not allow microbes to enter the container.

Testing for CCI in “normal” room temp storage is done by subjecting the sealed containers to stress conditions of temp and pressure to see if the vial or syringe will fail while being surrounded by a liquid broth of bacteria or an aerosol of bacteria at a high concentration....usually about 10^8 bacterial count. Also, the containers are challenged using both aerobic and anaerobic oraganisms and, sometimes, the packaging is ship tested in the field and then subjected to CCI testing.

In the case of frozen products, -80DegF in this case, CCI testing must account for the shrinkage that occurs in the cold. Glass does shrink. Rubber stoppers freeze solid and shrink. The ratio of shrinkage to container dimensions has to analyzed. If the stopper shrinks too much it will lose contact with the container walls and then when warmed for use, it may leak.

Syringes pose several technical difficulties unique to syringes. With them, there is NO retainer to keep the stopper in place other than friction. Over time, changes in temperature and pressure can cause the small air bubble in a syring to expand and push the stopper out. The change in air volume doesn’t have to be very much, just a couple of psig change during a air transport can cause the stoppers to rise and lose sterility.

There are many more technical issues related to container closure product development...such as the multiple injections (up to 10) from a single vial and the stopper has so many holes in it that it fragments and produces rubber particles...so much fun!

Don’t get me started on permeability of containers...they ALL breath during shelf life! Physics!

Any questions? Please advise.
GRRRRR

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