Thank you, this is helpful - I've edited the parent post to include some of your feedback.

About the community: the only other place I've found so far is /r/radvac - though pretty dead, it may be useful to find people connected to the community. This page also mentions a Boston RaDVaC group.

I understand Arg319-Phe541 to mean the subsection of the spike protein that begins with arginine at position 319 and ends with phenylalanin at position 541.

This seems right - the RaDVaC white paper has a nicely formatted copy of the S protein on page 40, and it begins with R / arginine at 319 and ends with F / phenylalanine at 541.

I found 230-01102-1000-RB by RayBiotech as a cheaper option. If you buy 100 µg of it at 308 € (includes 19 % VAT) you end up at 52 € per dose / 154 € per person. Or you buy 1000 µg at 1129 €, which is enough for 22 people, it's 18 € per dose / 52 € per person. Again, I have no clue about what you have to look out for when buying this peptide (e.g. format, purity, formulation, ...?) for an injected vaccine, any info on this would be highly appreciated!

Apart from that, the data released on the Stöcker vaccine shows that shots 1, 2 and 3 were on average 10 and 32 days apart. Storing the peptides for this amount of time does not seem to be trivial, see e.g. the storage requirements from RayBiotech for their Arg319-Phe541:

Upon arrival, the protein may be stored for 2 weeks at 4 °C. For long term storage, it is recommended to store at -20 °C or -80 °C in appropriate aliquots. Avoid repeated freeze-thaw cycles.

Maintaining 4 °C sounds doable with a good fridge and a data logging thermometer. -20 °C is more tricky - maybe use a home freezer (*** is specced at ≤ -18 °C) and add a data logger. If it then turns out that it can't reach -20 °C, it might be possible to fix that by modding its internal thermostat somehow. Or have access to a lab freezer, or shell out the big bucks (four figures) to buy one.

I am curious about the storage requirements for RaDVaC and couldn't find out anything specific on the webpage or in the whitepaper. Though the latter does mention some steps that were taken to improve peptide stability, it would be nice to have some info on this.

Good point! I've attempted to expand on this a bit, and list the advantages that each vaccine currently seems to have over the other:

For RaDVaC:

• Extensive Documentation, Whitepaper and reasoning about its development available
• Manufacturing does not require a sterile environment
• Simpler administration
• Has a small community, might be easier to exchange questions and results
• Regularly updated (possibly double-edged - seems very useful to keep up with any variant capable of immune escape, but may (?) make it more difficult to estimate efficacy across vaccine generations)
• Designed to prevent immune escape, may still work when commercial vaccines become less effective (uses 9 - 13 peptides instead of just targeting the spike protein like other vaccines)
• Cheaper ingredients, because the peptides required are shorter

For Dr. Stöcker's Vaccine:

• Test results released so far show very good efficacy and safety (for n=64)
• Known-good dosing regimen available
• Efficacy can be verified using commercial blood antibody tests
• Requires only one peptide (which might be orderable as-is, without custom synthesis) and two passive ingredients

One way to achieve sterility might be to use a self-made glovebox (example tutorial). For extra safety, you could also add an intake fan with a HEPA filter to get a positive-pressure sterile environment, which would still be sterile in case of a small enough leak. Or build a positive-pressure hood - more upfront work, but working in it seems easier.

Personally, the good results and self-verification capability (using antibody tests) would make me prefer Dr. Stöcker's vaccine despite the extra hassle, as long as we knew what kind of Arg319-Phe541 peptide we need for it.

Edit 1: Added / edited the last two points in the RaDVaC list, thanks to feedback by ChristianKl.

Cerascreen offers an at-home antibody test. You use the kit you buy to draw a small blood sample at home and mail it to them. They use the ELISA method to test the blood for IgG antibodies and show you the result on a webpage. Not sure if this is available outside Germany, though maybe a different company offers something like this where you live.

Abbott also produces a blood test for IgG/IgM antibodies, except that it comes with a small test cassette that gives you the result directly, without sending it to a lab. Maybe importing this (or something similar) is an option for you.

There is another Covid-19 peptide vaccine developed by a Dr. Winfried Stöcker. He injected it into ≥64 volunteers, and the results he published look promising. They show both a good level of IgA, IgG and IgM antibodies and ≥ 94% neutralization for the vast majority of the test subjects. According to him (last paragraph of his blog post), none of the test subjects have reported any relevant adverse symptoms.

He describes the manufacturing in his blog (see translation below):

Man nehme dreimal 15 Mikrogramm rekombinante RBD der S1-Untereinheit (Arg319-Phe541) für eine Person. Als Adiuvans habe ich Alhydrogel von InvivoGen verwendet: Ordentlich durchschütteln und davon 200 Mikroliter mit der Tuberkulinspritze aufziehen. In eine größere Spritze 10 Milliliter Kochsalz aufziehen und die 200 Mikroliter dazugeben, mischen. Davon 500 Mikroliter pro Schuss, mit denen man seine Portion Antigen vermischt. Alles hübsch steril.

I've attempted a translation and added some of my own understanding in [square brackets]. Though I'm a German native speaker, I have zero domain knowledge in this field, so please correct me if anything is wrong:

Take three times 15 μg [three doses of 15 μg per person, spaced days apart - see result data linked above for timing] recombinant RBD in the S1 subunit (Arg319-Phe541) for one person. As an adjuvant I used Alhydrogel by InvivoGen: shake thoroughly and then draw 200 μl with a tuberculin syringe. Using a larger syringe, draw 10 ml saline solution and add the 200 μl [of adjuvant], then mix. Of this mix, use 500 μl per shot and mix it with the antigen [the 15 μg recombinant RBD]. Do all this in a sterile way.

If (!) these instructions are exhaustive, it might be easier, though possibly more expensive to produce than RaDVaC. Googling Arg319-Phe541 suggests that 100 μg (6 doses) / 1000 μg (66 doses) of this RBD can be bought for 310 € (52 € per dose) / 1130 € (18 € per dose), though there may be cheaper offers. I have no clue if the Arg319-Phe541 RBD I found here (230-01102-1000-RB listed on biocat.com and raybiotech.com) would be of the right kind to use in a vaccine. 

If you have the relevant domain knowledge to evaluate how complete these instructions are or what other risks and benefits compared to RaDVaC this vaccine may have, I'd really appreciate a comment. Likewise (and especially) if you know where to buy the kind of Arg319-Phe541 RBD used for this vaccine.

If you speak German or are comfortable with DeepL: the current edition (06/21) of the German magazine "Der Spiegel" has some more background on its development on pages 44 - 46: PDF (available for free due to misprints).

Edit 1: Detailed serological results (in English) were posted by Dr. Stöcker in May 2020 when he tested the vaccine on himself first.