August 20th: Unfortunately, declining vaccination rates, a move to booster shots, and the failure to shift vaccine supplies from developed countries to developing ones have all combined to significantly push back the worldwide timeline. Vaccine rates have fallen to 16.5 million doses / day and the latest estimate is now Feb 16, 2022.

August 6th: The US plans to give booster shots to immuncompromised citizens - link.

August 4th: Vaccine distribution continues to progress and is now up to 23.5 million doses per day.

August 3rd: Germany announces a vaccine booster program.

August 2nd: The UK announces that they will give booster shots to 20 million of the population above the age of 50. This is in response to the decreased effectiveness of AstraZeneca to the Delta variant and will delay the overall vaccine timeline by about one day.
August 1st: The worldwide vaccine program (excluding China) has hit its fastest rate yet, 21.5 million doses per day. This has led to a shortening of the worldwide timeline by almost 20 days.

How do you calculate the forecasts?

I use vaccine data from Our World in Data and population data from the UN (links at bottom). For each country, I take into account the total adult population, how many are fully vaccinated, partially vaccinated, and unvaccinated to calculate how many doses are needed; and I use the 7-day smoothed vaccination rate as the denominator.

For example, in the United Kingdom, about 1.5 million doses more are needed, and doses are being at a rate of 245000 per day, which means that the 70% vaccination target should be reached in about 6 days.

Worldwide, as a rough estimate, currently about 4 billion more doses are needed for 70% of the world's adult population to be fully vaccinated and about 40 million doses are being given per day.

Note: For the worldwide clock, data is at a country-level and any additional vaccinations beyond 70% are not counted, so the target will not be reached by some countries vaccinating 90% while others vaccinate 50%.

Really, so soon?

I was also surprised. The above estimate assumes that vaccinations will continue at the current rate, which means that as countries vaccinate their population, vaccine supplies will move from mostly vaccinated countries to mostly unvaccinated ones.

Can it take longer?

There are several reasons why it could be. Boosters may be necessary to combat new strains. Children may need vaccines which will increase the total population that needs vaccines. Finally, new variants may arise which would require significant re-vaccination.

Or quicker?

Certainly. The speed with vaccinations are being distributed is on a mostly upward trend. Supply and logistics are improving. When I started this project, about 10 million doses were being given per day, and that has increased to 20 million / day now (without China) or 35 million / day (with China). Also, new vaccines are coming on-line (for example, see Novavax's announcements of Phase 3 results and the construction of their Canadian manufacturing center).
Finally, I have omitted China from the overall calculation because it is not clear how exportable their vaccines will be after the vaccination program is complete in China. If the Chinese vaccines are deployed elsewhere after their vaccination program is complete, then that will almost halve the total amount of time it takes to reach our vaccination program. Currently, about 4 billion doses are needed worldwide and of the 35 million being distributed per day, an astounding 15 million of those doses are being given in China, which could reduce the overall timeline to about 125 days.

Why 70% of adults?

I am particularly interested in these thresholds because vaccination programs take a "S"-shaped curve over time. In the beginning, there are supply constraints which slow down the distribution of vaccines. As supply and logistics improve, the vaccination program speeds up, until a large percentage of society is vaccinated, whereupon vaccination rates slow down due to vaccine hesitancy. This hesitancy threshold differs significantly from country to country, but the maps below model the first two stages of the vaccination programs before hesitancy becomes the limiting factor.

Which countries have reached the target?

Aruba, Bahrain, Bemuda, Cape Verde, Cayman Islands, Chile, Gibraltar, Guernsey, Iceland, Isle of Man, Israel, Malta, Mongolia, Saint Helena, San Marino, the Seychelles, and the United Arab Emirates.

Who is close?

The following countries are all within 10 days of the target:

the Falkland Islands, Jersey, Qatar, United Kingdom, and Uruguay.

And a little further?

The following countries should reach the target within 11-30 days:

Andorra, Anguilla, Austria, Belgium, Canada, China, Denmark, Faeroe Islands, France, Germany, Greenland, Ireland, Luxembourg, Nauru, Netherlands, Portugal, Saint Kitts and Nevis, Singapore, Spain, and the United Kingdom.