Vaccines against SARS-CoV-2 are proving quite safe and highly effective in the prevention of COVID-19, especially severe and/or fatal disease. Over half of the U.S. population has initiated immunization and more than three out of four people in the U.S. over the age of 65 have completed vaccination. The promising vaccine roll-out and reductions in the U.S. incidence of COVID-19 cases, hospitalizations, and deaths have led to an admixture of two competing reactions: optimism that we are nearing the end of this nightmare countered by concern about viral variants that are sprouting up with discomforting regularity.
An increasing refrain is that we need to get ready for vaccine boosters to prevent a resurgence in cases. While I certainly anticipate rolling up my sleeve for an anti-SARS-CoV-2 booster, we simply don’t know when that will be. Right now, we need to focus on vaccinating more people nationally and globally and preventing the spread and emergence of variants.
While we do not know how long meaningful (clinically-relevant) vaccine-induced immunity against SARS-CoV-2 infection will last, it seems to be on the scale of 8 to 12 months, if not longer. Thus, if the pandemic were to completely end during the next year, we might be able to hold off on booster shots, firing them up only if any new COVID-19 hotspots arise. But, it seems clear from the ongoing activity of COVID-19 in many parts of the world that the pandemic is far from ending anytime soon. And SARS-CoV-2 variants just keep coming.
The latest cause for concern? The Delta variant (B.1.617.2, first recognized in India), which is now the predominant SARS-CoV-2 virus in the U.K. and gaining ground in the U.S. This variant appears to be more contagious and more dangerous, but fortunately, it appears that currently available two-dose vaccines provide good coverage against it. Regardless, vaccine manufacturers such as Moderna and Pfizer-BioNTech are launching programs and clinical studies to prepare for booster shots targeting variants of concern.
It might seem tempting to some, in the absence of formal recommendations, to get an “extra” (booster) vaccine dose (with existing vaccines currently in use) sometime in the 6 to 12 months following an initial vaccination regimen. Could this be a path toward longer and stronger immune protection against the threat of a new wave of COVID-19 activity? For now, I warn against this approach (outside of rare exceptions related to revaccination of immunocompromised persons who may require extra doses to stimulate measurable antibody responses). Here is why: we need to use our existing vaccine supply to immunize, rather than re-immunize, people both in the U.S. and abroad.
The pandemic remains red hot and active in many countries where a majority of people are unvaccinated (and vaccine supplies are limited in many regions). Recent efforts from well-vaccine-resourced countries (like the U.S.) to deploy vaccine supplies to these vaccine-limited settings are critically important. Controlling the pandemic will translate into lower chances that new SARS-CoV-2 variants emerge and spread. In this way, vaccinating the far corners of the globe will delay or defray our need to get boosters here.
When it comes to the U.S., if new or existing SARS-CoV-2 variants gain a foothold here, we need to be sure that as many people as possible have completed vaccination. Knowing that currently available vaccines are protecting against severe disease and death caused by recently emerged variants should motivate us to get as many eligible people immunized as we can. And while we don’t yet have a complete understanding of the extent to which the single-dose J&J shot protects against the Delta variant, it is still important to keep our eye on the ball with our available vaccines: get them into people who have yet to initiate vaccination. A major goal of mass vaccination is to make it hard for the SARS-CoV-2 virus to find susceptible victims. Unfortunately, many eligible persons in the U.S. have yet to initiate vaccination. This is a much more important population for our focus than boosting fully vaccinated people.
How best can we do that? Well, certainly we need to get the vaccines to the people; that means mobile vaccine units, pop-up clinics, and empowering more clinics, pharmacies, and public health facilities to provide shots. As recent data inform us, we also need to change the minds of young people who remain reluctant to get immunized, dispel myths about the vaccines (they do not cause us to become magnetic, by the way!), and work to depoliticize both the disease and the solutions.
There may come a time when we are strongly compelled to begin administering booster shots, either with existing vaccines or new variant-targeting ones. But that time is not now. Let’s help get the unimmunized in the U.S. and abroad protected as soon as we can. Slowing the pandemic through widespread immunization is our key to delaying the need for booster shots.
David M. Aronoff, MD, is Director of the Division of Infectious Diseases in the Department of Medicine at Vanderbilt University Medical Center.