On Friday, the Biden transition team announced they are releasing all the available vaccine doses.
Both FDA-approved vaccines require a second dose 21 days (Pfizer-Biontech) or 28 days (Moderna) after the first in order to achieve the greater than 94% efficacy in COVID-19 protection. A third vaccine (AstraZeneca-Oxford) approved in the UK and India, also requires two doses, initially 28 days apart, with greater than 90% efficacy.
Eight governors recently wrote a letter to the current administration requesting the release of all available vaccine doses to states. Until now, the federal government had been maintaining a stock of half of the available vaccine doses in order to ensure adequate supply for second doses.
Releasing all the doses at once means there is a risk that the people who get the first dose may not get the second dose at the scheduled time. The Biden team has asserted confidence that supplies would be adequate, or that they could invoke the Defense Production Act to increase vaccine production if needed.
Several scientists in both the US and UK have already proposed that second doses be delayed to 12 weeks rather than 3-4 weeks in order to increase the first dose. Getting only one dose does provide partial immunity (52.4% efficacy for Pfizer-BioNTech, but this may increase to over 85% after 10 days or more) but not the full >94% provided by the second dose. It is also unknown if the protection provided by the first dose will be long-lasting without the second dose—the study only monitored for 21 days.
Delaying second doses is a wager that, in the setting of such severe shortages and limited data, getting more people partially immunized quickly will have better outcomes compared to getting fewer people immunized fully.
For the Pfizer-BioNTech and Moderna vaccines, there is no evidence for or against this strategy. The only data is from the clinical trials themselves, which only assessed one schedule (two doses within a month). However, in the UK, studies of the Oxford-AstraZeneca vaccines included a subset that had longer gaps (8-12 weeks), which indicated greater immune response. However, this was a smaller group so it is difficult to tell how robust this result is. It is not clear if the same will be true for the Pfizer-BioNTech or Moderna vaccines.
There is some evidence that those with prior infection with “natural” immunity have sustained protection for at least 12 weeks or more, so it is reasonable to hypothesize the same might be true for a single vaccine dose. For other infectious diseases, such as with many childhood vaccinations we have seen a little bit of flexibility with “catch up” immunization scheduling, but the CDC discourages excessive delay.
The European Medicines Agency has suggested that for the Pfizer-BioNTech vaccines, the second dose should not be longer than 42 days. In contrast to UK and European officials, the US FDA has strongly discouraged changing the dosing schedule, noting that such changes without data is premature. As of this writing, now 22.1 million doses have been distributed, and 6.7 million doses have actually been given to people.
It is unclear that the primary barrier to vaccine access is the availability of doses. Distributing vaccines is an enormous logistical challenge even in the best case of centralized health systems and coordination. In the US, this is made even more challenging in a large country with a heterogeneous and fractured health system. Even so, the distribution has been accelerating. There is also the other concern about uptake—even as vaccine doses get sent out, people must accept them. Even among eligible healthcare workers, a large percentage have opted not to receive the vaccines, at least not right away. This may improve with time and more and more people receive the vaccine.
Dr. Anthony Fauci, head of the infectious disease division of the NIH has cautioned against any delays or tinkering with the vaccine schedule, primarily as it could further erode public trust.
Currently, things are dire—Los Angeles County is looking at the worst-case scenario of rationing acute medical care. A new variant of the mutation has accelerated the spread of an already highly contagious virus. Despite record-breaking numbers of infections, hospitalizations, and deaths, it is likely we have not seen the worst of this surge. The spread of the virus to parts of the world with even fewer resources could be even more catastrophic than what has already occurred.
The uncomfortable truth is that public health authorities and leadership must make rapid decisions with profound consequences with limited information. They must do this with transparency and informed by the best available science and ethical considerations. That this public discourse is also heavily politicized, rife with misinformation and mistrust, complicates this.
There continues to be a long road ahead. Even so, in less than a year, a brand new infection was sequenced, and effective vaccines were delivered into the arms of people. Front line medical staff have drastically reduced the mortality rate of patients. Billions of people have cooperated, sometimes with great personal sacrifice, to slow the spread of this infection. This continues to be astonishing.
Dharushana Muthulingam, MD, MS, is an infectious disease physician and public health researcher in St. Louis.