Understanding the Debate Over Covid Booster Shots

With the especially contagious delta variant threatening efforts to end the pandemic, a growing number of wealthy countries are planning to or considering administering booster shots of Covid-19 vaccines, at least to particularly vulnerable groups. U.S. regulators said Sept. 22 that people 65 and over and others at high risk of severe Covid or Covid complications can receive a third dose of the Pfizer Inc.-BioNTech SE vaccine. Officials at the World Health Organization have characterized the wide rollout of boosters in wealthier countries as unethical as long as poorer countries still lack supplies to cover significant portions of their populations with initial doses.

The term traditionally has referred to an additional dose of a vaccine given some time after the initial course of inoculation to bolster protection that may have started to wane. While many vaccines produce long-lasting immunity, the U.S. Centers for Disease Control and Prevention recommends that adults receive boosters of the tetanus vaccine every decade, for example. For Covid-19, a new disease, researchers are working out the optimal schedule and dosage for a wide variety of vaccines on the fly in the midst of an ongoing pandemic. The term booster is being used loosely to refer to additional shots given for a variety of reasons to people who have already received the prescribed course of a Covid vaccine, meaning one dose of Johnson & Johnson’s formulation or two doses of any of the others. With the messenger RNA vaccines, the first two shots were given relatively close together, either three or four weeks apart. If an additional dose is given six months or so after the first two, it may produce longer-lasting immunity, by training the immune system to realize that Covid is a long-term threat.