On 4 August 2021, Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization, called for a global moratorium on booster doses of vaccination against COVID-19, until the end of September, with a goal of having 10% of every nation’s population vaccinated. This comes on the heels of both Israel and Germany starting vaccine campaigns of a third dose, and provinces such as Quebec, Canada, giving third doses to provide an easier pathway for international travel. In the United States, on 12 August 2021, the US Food and Drug Administration authorized booster doses for certain immunocompromised people.
As more rich nations consider boosters, their local public-health communities need to wake up to the widening chasm of vaccine inequity and its devastating consequences, especially with the Delta variant ripping through populations. All of us need to look within and ask hard questions. Are we as a species willing to protect all humankind, or do we mostly care about optimizing protection for people in wealthy nations?
Any discussion of booster dose strategies requires an application of scientific as well as equity principles.
From a scientific perspective, a key question is how long the immune response to the mRNA vaccines lasts. Data from Pfizer show efficacy of 84% after 4 months for symptomatic COVID-19, with 97% protection against severe disease1. The Moderna vaccine has shown efficacy of over 90% at 6 months against symptomatic COVID-192. Although data on the vector-based immunizations are lacking, experiences from the United Kingdom show that the majority of complicated COVID-19 cases exist among the unvaccinated, rather than those who received the AstraZeneca vaccine3. All approved vaccines seem to show reasonable efficacy against symptomatic and severe disease after infection with the Delta variant in datasets from the United Kingdom4 and Canada5.
As new variants emerge, breakthrough cases emerge, and a small number of these patients will develop complications, but no data exist that link boosters to enhanced real-life protection in the general population. Other than rare immunosuppressed patients, such as organ-transplant recipients6, the vast majority of the population, including the elderly and those with medical conditions, derive adequate protection from the existing vaccine schedule. Vaccinating the unvaccinated can save many more lives than would boosting people who already have a fairly high level of protection.
