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The evidence is mounting that the COVID-19 vaccines are working to drop COVID case numbers and hospitalizations at record paces. The country is already seeing results, and with Johnson & Johnson gaining approval for their single-shot COVID vaccine this weekend, the numbers of vaccines being shipped every week hitting record levels. States like Texas are getting over half a million doses this week alone.

As the numbers of vaccines being shipping increases, and the numbers of those vaccinated increases as well, the end of the pandemic is coming into focus of many. But there are still some who are worried about the countries vaccine supply.

While I was watching video of the semi trucks full of vaccine pull away from a Johnson & Johnson facility in Kentucky, I was thinking about how much vaccine could fit on one of those trucks. Then I started building a frame of reference for how much vaccine is needed to vaccinate the whole US.

I'm going to do this math from the start, pretending that there haven't been any doses of the vaccine given out, or anyone with antibodies after recovering from COVID.

There are just over 200 million adults in the United States. We know COVID-19 doesn't impact children under 18, which is part of the reason that the FDA and CDC have not cleared COVID vaccine use on those under 18. So we'll be working off the number 2.9 million.

Looking at how big vials of the vaccine are can be a little tricky. We're working with three different vaccines, so the sizes will be slightly different. But they're all roughly the same size. What I did was go to the World Health Organization's manual on cold storage vaccines, where they list dose sizes between 2.1 cubic CMs, and 3.1 cubic CMs. In the WHO breakdowns, they don't list specific vial size, but "dose" size. We can make our math a little easier by averaging them to 2.5 cubic CMs, because then we can convert it to an easy 1 cubic inch.

So each dose will take up 1 cubic inch in our hypothetical semi trailer. Again, that's not a viral size, that's for each dose.

According to B&W Trailer Rentals, each 48 foot semi trailers has a capacity of 3,465 cubic feet. So now we can get down to the math parts...

Each truck can hold 3,465 feet (cubic), which means 41,580 cubic inches. Based on the average that we took from the WHO of 1 cubic inch for each dose, it means we can fit 41,580 doses per semi trailer.

With some vaccines requiring two doses, we'll have to find an average number to vaccinate Americans. If we split the three vaccines evenly, with two needing second shots, we'll need closer to 5.5 million shots, so we can work off that number.

If each trailer holds 41,580 doses, we'd need about 132 trailers to hit 5.5 million doses.

That's the max number too. Because if we start to take into account all of those who have already recovered from COVID-19, including the massive amounts of asymptomatic people, we will really need much less than the full compliment of metaphoric trailers of vaccine.

That number, 132 trailers, was also what we would have needed from the start. We've already had millions of doses already used, which drops the number we still need. So even if we started with 132 trailers needed, we're probably closer to 50-60 trailers needed. Which is an interesting way to think about this pandemic...we're about 50 semi trailers away from being completely done with the pandemic.