COVID-19 Vaccine Distribution Tracker: Week of March 22

Editor's note: Below you'll find release of the COVID-19 Vaccine Distribution Tracker originally published March 23, 2021. Visit the COVID-19 Vaccine Distribution Tracker homepage for the latest data.

States are in a race against time to expand COVID-19 vaccine eligibility. May 1 marks the deadline set by President Biden to make doses available to any U.S. adult who wants one. But scaling up distribution so rapidly may not necessarily be sustainable—and it may not be moving the needle. 

The government delivered another 21 million doses to states over the last week, only a slight increase from the weekly 20 million we’ve been seeing since Johnson & Johnson entered the scene at the end of February.

While Biden has pledged more doses, the current cadence is not enough to make good on his promise “to have enough vaccine supply for all adults in America by the end of May.” (Note: We interpreted “enough supply” to mean enough vaccines to account for two full doses of Pfizer and Moderna shots, not just the first dose.)

Right now, Wyoming is the only state or territory on track to have enough doses to fully vaccinate its adult population by the end of May.

In the meantime, we can look at the available data in a more promising way. Which states are vaccinating people efficiently enough that, if patterns from the last seven days held, a meaningful majority (70%) of the adult population would be fully immunized by the 4th of July? As of March 22, at least four are on target: Delaware, Vermont, New Mexico, and California.

Why 70%?

While there’s still no clear percentage of the population necessary to reach herd immunity for COVID-19, 70% is a good place to start. Herd immunity refers to the protectiveness achieved when a significant portion of a population develops immunity to an infectious disease, either through vaccination or having a prior illness. Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, used to say 60% to 70% of the population needed to be vaccinated or recovered to reach herd immunity, his projection has evolved to range from 70% to 90%.

Herd immunity is a complex calculation that relies on both past infections and number of people vaccinated. Because the World Health Organization emphasizes herd immunity should rely on vaccination and not disease exposure, for the sake of projections, our numbers focus on the time it will take to hit 70% through vaccination alone.

Last week, four completely different states were targeting the July 4th benchmark: Maine, New Jersey, Pennsylvania, and Rhode Island. The volatility can be explained by the massive and sudden eligibility changes happening in different states.

According to the New York Times, at least 20 states will open vaccine eligibility to all adults in March or April. Alaska and Mississippi already have. Last week, specifically:

  • Delaware lowered the eligibility threshold to adults ages 50 and older, as well as anyone age 16 and older with an underlying health condition.
  • New Mexico, a state that has steadily cruised through vaccination of eligible adults, officially entered Phase 1C—the last distribution phase before vaccines become available to everyone.
  • Vermont began offering vaccines to anyone age 60 and older.

When more groups become eligible for their first dose of a COVID-19 vaccine, the long-term outlook for a state becomes better—after all, herd immunity relies on an increase in the total number of people vaccinated. Therefore, an increase in first doses nudges a state a little further along the herd immunity timeline than an increase in second doses.

The challenge is having enough vaccine supply to continue putting shots in newly-eligible arms. And as the (very short) history of the COVID-19 vaccine rollout shows, slow and steady may actually win the race. 

States like Alaska, Hawaii, New Mexico, and Connecticut have kept their eligible populations fairly narrow throughout the bulk of the rollout, expanding a little at a time. As a result, two things are true. First, more high-risk people are vaccinated in these places. And second, these states are also equipped to maintain high efficiencies when it comes to administering their available doses to even wider groups of people.

Data by Amanda Morelli/Adrian Nesta

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  1. World Health Organization. Coronavirus disease (COVID-19): Herd immunity, lockdowns and COVID-19. December 31, 2020.