When retired Gen. Colin Powell’s family announced his death Monday in a brief Facebook post, they said that the cause was “complications from Covid 19” despite being “fully vaccinated.” The former secretary of state, who was 84, had also been undergoing treatment for multiple myeloma. That kind of cancer causes marked impairments of the immune system, rendering it capable of producing only one type of antibody. In July, a study of vaccinated people with multiple myeloma found that only 45 percent had immune responses that would be “adequate” to protect them against covid. A booster dose is recommended for people with blood cancers, but no amount of vaccination can make up for an immune system that can’t fight back. To the medical community, it was no surprise that Powell could develop a severe, even fatal case of covid-19.

Much of the discussion surrounding his death, however, suggested otherwise, as if this was a case of some irregularity or failure of the vaccines. That specific phrase — “fully vaccinated” — stood out to me especially, as it featured prominently in most news coverage. It implied that Powell should have been completely protected; that he shouldn’t have been able to die from covid-19. The use of “fully vaccinated” is not unique to Powell, either, though the coverage of his death has highlighted that the term is inappropriate in many cases, primarily because there is no consensus on what it means. As we’ve seen throughout this pandemic, precision of language and transparency in delineating the known and the unknown are key to any effective public health response. A sense of false confidence — or of exaggerated risk — can permanently damage the credibility that is so critical to the success of the coronavirus vaccination campaign and of future ones.

At the moment, the central debate among immunologists and infectious-disease experts — in the United States, at least — pertains to booster doses. It has become clear that some people will benefit from additional shots (third doses of the mRNA vaccines and second doses of Johnson & Johnson) and equally clear that others may not. The challenge is in determining where to draw that line. Most of us fall into a gray area between the 21-year-old Olympic decathlete in no need of more doses and the 90-year-old with emphysema who sings in an unvaccinated choir and would quite benefit from boosting.

All of this boils down to, essentially, an ongoing attempt to define “fully vaccinated.” Who is “fully vaccinated” against covid-19, and for how long? The honest answer is that the target is moving before our eyes.

Until 2021, “fully vaccinated” was not a standard phrase, any more than “fully married” or “fully graduated from college.” Typically a person is considered “vaccinated” or “unvaccinated.” Technical distinctions might be used clinically to describe gray areas — a young child or a puppy, say, between doses of measles or rabies vaccines, may be considered “partially vaccinated” for purposes of logistical communications between doctors. But such a designation would not imply that the child or puppy is protected.

Early this year, as coronavirus vaccines began to become available to the public, the term was useful — a way to distinguish between those who had gotten only their first dose of an mRNA vaccine and those who had received the full two-dose regimen. Ten months later, abundant new evidence has actually made it less clear whether our vaccine regimens should consist of one, two or three doses. Currently, the Centers for Disease Control and Prevention says people are fully vaccinated “2 weeks after their second dose” of Pfizer or Moderna, or “2 weeks after a single-dose vaccine” such as Johnson & Johnson. This definition is already obsolete; as of last month, the agency also recommends third doses of the Pfizer shot for high-risk groups after six months. Soon the recommendation is expected to extend to everyone over 40. There is legitimate disagreement among experts, and important debate as to the prudence of such a move, all part of the attempt to define “fully vaccinated.”

Much of the focus on the fact that Powell died despite being vaccinated is surely opportunistic, intended to raise doubts about the effectiveness of the coronavirus vaccines (and, thereby, the medical, public health and scientific establishments). Bad-faith interpretations of morbid outcomes are nothing new: Whenever a person who received a vaccine experiences an adverse effect, profiteers imply a causal relationship. This happened from the very first reports of extremely rare blood clots, and it continues now when vaccinated people fall ill with covid-19.

But beyond pandering to far-right audiences and conspiracy theorists, the reports on Powell’s vaccination status play into genuine concerns about “breakthrough infections” in high-risk people. (Individual narratives can be more compelling than 99 percent of statistics, according to my mechanic.) Such anecdotes become even more influential when official messages seem to be misleading or contradictory: I thought I was fully vaccinated; now you’re saying I’m not? If vaccines work, why can a fully vaccinated person still die?

The answer is that they can still die in the same way a person who is “fully seatbelted” still can. The degree to which any of us are protected by vaccination depends on more than simply how many shots we receive and how effectively our immune system responds. It also depends on those around us. In Israel, as of this month, officials require everyone to have three doses to be considered “fully vaccinated,” and they’ve secured fourth doses for each citizen as the virus continues to spread. Unvaccinated people there have been hospitalized at three times the rate of their vaccinated neighbors. But wherever people remain unvaccinated, we may see high-risk groups debating fifth or sixth doses. This would be akin to wearing a fifth or sixth life jacket while others still have none: not merely unjust, but far less effective than making sure everyone has one jacket. And shipwrecked people can still suffer from hypothermia or dehydration or heart attacks, no matter how many life jackets they manage to fit on. The fact that vaccinated people are dying of covid-19 in the United States reflects no greater failure than that of everyone else to get their shots and drive the virus into obscurity.

If “fully vaccinated” is useful as a concept, it’s more at the level of the population than the individual. There is probably no amount of vaccine that can guarantee an 84-year-old with blood cancer is absolutely protected from covid-19 — or from anything else. When people are old and sick, even a mild illness can push them over the edge into respiratory or cardiac failure. The goal of vaccination is to drive a virus out of a population. This means everyone getting their first and second doses so that everyone is functionally protected.

To be fully vaccinated might more accurately be the goal of a school or business or town or nation. And ideally, of the world. The more we lose sight of this, focusing instead on boosters and some ethereal notion of a “fully optimized individual,” the more we stand to lose, and the longer the pandemic will linger, with doses hoarded and layered on high-risk people — while the unvaccinated blame the continued spread of the virus on the vaccines, rather than on themselves.

Twitter: @jameshamblin