Scaling and Stretching the Supply of COVID-19 Vaccines
While the commencement of the U.S.’s COVID-19 vaccination campaign has brought a much-needed positive news cycle, the realization that supply will be limited for many months is a reason for some emotional restraint. The Food and Drug Administration’s emergency use authorization for the Pfizer-BioNTech mRNA-based vaccine last week, and the approval of Moderna’s mRNA candidate this week, are important steps on the road to the pandemic’s end. But production ceilings mean that the U.S. will continue to experience the effects of the pandemic well into 2021.
Currently, the U.S. has secured a combined supply of 300 million vaccine doses from the two mRNA manufacturers — 100 million from Pfizer and 200 million from Moderna. As each vaccination requires the administration of two doses per person a few weeks apart, the purchase agreements in hand are sufficient to guarantee protection for only 150 million people, or around forty-six percent of the overall U.S. population (this calculation may be altered modestly by the news that some Pfizer vaccine vials contain an extra dose or two).
Public health experts believe that herd immunity will not occur until, at a minimum,70 percent or more of the country — about 230 million people — has been vaccinated or recovered from a natural infection. The Centers for Disease Control and Prevention (CDC) estimates that around 53 million natural infections occurred through September 2020. Since then, the overall number of confirmed cases has more than doubled, so it is possible that upwards of 100 million people may already have been infected by the virus. However, because it is not known with certainty how long immunity lasts for those who have been infected, public health officials are recommending vaccination for everyone, including those who have recovered from COVID-19. Thus, the U.S. is planning to reach herd immunity through vaccination but has not yet secured sufficient supplies to ensure that objective can be reached in the first half of 2021.
The lead officials overseeing the U.S. vaccine procurement effort expect other vaccine candidates beyond Pfizer and Moderna to gain approval and fill in the supply gap starting this spring, but that is no sure thing. Early data from the Phase III trial of the two-dose AstraZeneca-University of Oxford candidate suggest it may not be as effective as those developed by Pfizer-BioNTech and Moderna, and there is no efficacy signal yet for the one-dose J&J candidate. As has been noted often, vaccine development is a high-risk endeavor, and any number of problems might arise in the coming weeks to rule out the use of these vaccine candidates in the first half of 2021.
Given the stakes, health officials should be looking at every possible option for accelerating the manufacture and distribution of the mRNA vaccines. For example, the White House has signaled a willingness to invoke the Defense Production Act as necessary to support the production of vaccine ingredients, materials for “cold chain” logistics, and necessary devices for vaccine administration if it helps speed up the vaccination process.
What should not be done at this point is to diverge from the dosing protocol tested in the Pfizer and Moderna trials, as was suggested in a recent Wall Street Journal op-ed. The proposal was to spread existing purchases across more people by giving just one dose to lower risk individuals and postponing the administration of the second dose until more abundant supply is available.
Unfortunately, the data from the Pfizer and Moderna Phase III trials do not support adoption of this strategy. While it is certainly possible that one dose might offer sufficient protection for low-risk individuals, nearly all participants in the Phase III trials received a second dose a few weeks after their first injection, as planned. The fact that COVID-19 rates across the placebo and vaccinated trial groups diverge 14 days after the first injection means that there is likely temporary protection from the disease after just one dose, but the test provides limited information about the counterfactual in which the second dose was not administered at all or was substantially delayed. Moreover, many vaccine experts believe two doses of the mRNA candidates will be necessary to ensure the protections is sufficiently durable.
Even so, the fact that one dose might offer temporary protection from the disease means that the potential to stretch limited production capacity by delaying the administration of the second dose may be worth further investigation, as an insurance policy in case other supply does not come online soon enough. For instance, it is possible that the other vaccine candidates will fall well short of the observed efficacy rates for the mRNA vaccines and thus be far less desirable to the public. Under such a scenario, health officials might be forced to make hard choices about how to maximize the public health protection from the available supply of more effective mRNA vaccines.
What is most preferable, of course, is to follow what has been tested to date, which is two doses of the mRNA vaccines for every American. Further, the value of widespread vaccinations is hard to overstate, in terms of protecting vulnerable individuals from infection, accelerating the societal protection that comes from herd immunity, and giving people the peace of mind that it is safe to resume normal activity. The U.S. government should use any and all methods for encouraging additional production capacity to come online as soon as possible, and for distributing the vaccines to the public quickly and safely.
Those efforts still might leave us short of sufficient doses, and there is always the chance that something else might go wrong and leave the country well short of the supply needed to reach herd immunity. With that in mind, it would be better to know sooner rather than later if stretching whatever supply is available over more people might be better than the alternative.
James C. Capretta is a resident fellow and holds the Milton Friedman chair at the American Enterprise Institute. Scott Ganz is a research fellow in economic policy studies at AEI and an assistant professor at Georgia Tech’s School of Public Policy. They are the authors of “Awaiting the Signal: Assessing the Efficacy of COVID-19 Vaccines,” published by AEI.
