I’m a college student, and I recently learned that my city is going to be opening up spots on the Health Department website for anyone to be vaccinated if there is a surplus of vaccines. We’re still in the first phase of vaccination, but if I were to look frequently at the vaccination website, I could in theory get an appointment.

Since I am a healthy, young person who is not an essential worker or at risk, should I wait to get vaccinated in hopes that someone at greater risk or more essential could take the spot? Or should I keep looking at that website and take the dose as soon as it appears? I’m not taking someone else’s spot, or am I? Ben, Montana

With anything perishable — whether it’s a head of lettuce or a defrosted carton of Covid-19 vaccines — you can have excess and spoilage amid an overall shortage. The minimum Pfizer vaccine order is a tray with about 1,200 doses; once the vials begin thawing, they have to be used in five days. With all the authorized vaccines, a vial, once opened, must be used within six hours — for Johnson & Johnson’s, it’s two hours at room temperature. Each Pfizer vial has up to six doses. Johnson & Johnson, which has a minimum order of 100 doses, puts five doses in a vial; Moderna will soon put 14 doses in each vial.

The point is that vaccines don’t come as “loosies.” Vaccination sites can misjudge the number of sign-ups, and even if everything is properly planned, there are sometimes no-shows. Even when a site has a standby list of qualified recipients, there will be occasional instances in which a vaccine will go to waste unless the eligibility rules are suspended.

Perhaps the question isn’t whether you’d be taking someone else’s spot but whose spot you’d be taking. I think of the verse that we apparently owe to the 19th-century English jurist and wit Charles Bowen:

The rain, it raineth on the just
And also on the unjust fella.
But chiefly on the just, because
The unjust steals the just’s umbrella.

In a situation where expiring vaccine doses will be offered to all comers — lest they simply go to waste — you have no reason to think that the dose you eschew will go to someone in greater need; if those concerned with justice demur, the dose may simply go to those not so concerned, assuming it goes to anyone. There’s always going to be a trade-off between getting the country swiftly vaccinated and exquisitely fine-tuning the rollout to reflect each person’s risk profile. If a sporadic all-comers approach is the best way to prevent wasted doses, it isn’t unfair, and you’re not wrong to participate in it.

There’s always going to be a trade-off between getting the country swiftly vaccinated and exquisitely fine-tuning the rollout to reflect each person’s risk profile.

There’s one other thing to bear in mind. Although you’re very unlikely, at your age, to become seriously ill with Covid-19, you can still spread it. In fact, it’s not uncommon for people who never show serious symptoms of the disease to transmit the virus. The available evidence suggests that once you’re vaccinated, transmission is less likely, perhaps much less likely. As with wearing a mask, then, your getting vaccinated helps protect others as well as you. It’s much better that a dose goes into your arm than into the trash.

I live in a state that is prioritizing vaccinations for those over 65 and anyone over 16 with chronic health conditions. As elsewhere, the rollout has been less than smooth: It has been reported that last weekend, when the county announced that it had 9,000 appointments available, it received over 30,000 simultaneous phone calls. There is no “proof of chronic condition” required, and our state has made it clear that it is trusting in the honor system for those seeking vaccination.

I’m 44 years old and reasonably healthy. I’ve been overweight since childhood. At times in my adult life, I’ve been much heavier than I am currently, which is hovering right at the border between “overweight” and “obese” (classified as a B.M.I. of 30 or higher; I’m around a 29 right now). My state considers anyone who is classified as “obese” to be in the priority group for vaccinations. Is it ethical for me to bend the definition of “chronic condition” and, in theory, jump ahead of someone else who might be in a much higher risk category? Name Withheld

You’re asking whether you may lie to get vaccinated quicker. My answer is: No. But there’s an interesting question you didn’t ask. Would it be OK to go on an eating binge to get your B.M.I. up to 30? In this scenario, you wouldn’t be prevaricating when you applied for an appointment. Surely, though, you’d still be abusing the system. Any criterion that can be hacked like that is problematic precisely for this reason. To be sure, the B.M.I. thresholds that states use (in some it’s 30; in others 40) are inherently arbitrary: A study in The Proceedings of the National Academy of Sciences last fall suggested that the rate of hospitalization for Covid-19 increases with our B.M.I. in linear fashion, starting with those only modestly overweight. That suggests that keeping yourself at a healthy weight rather than raising it may be the better option.

I have worked at farmers’ markets in New York City for many years, but since the pandemic struck, I’ve transitioned to full-time communications work at a church (producing their new livestream, among other things) and put in just one day a week at the market. As a market worker, I’m newly eligible for the Covid vaccine. I want to get vaccinated as soon as possible, for my own safety and for the good of everyone, but in truth my work and lifestyle enable me to stay quite isolated and safe from infection. Aside from my obvious advantages — or better put, privileges — of being highly computer literate, fluent in English and having the time to navigate the byzantine vaccination system, I feel that my limited exposure as a one-day-a-week essential worker makes my claim to vaccination doubtful. I want this vaccine to be rolled out in an ethical manner, and ideally privilege won’t play a role in it. But is eligibility eligibility, plain and simple? Damon, New York

What’s important is to try to remove barriers to vaccination — including those posed by not having access to transportation, to the internet or to English. Enlisting churches and other community organizations can help reach the city’s underserved and sometimes vaccine-hesitant populations. In fact, your work with the church might enable you to assist here. Once a reasonable system is in place, however, eligibility is, indeed, eligibility. You’re not proposing to use any inside connections to jump the line. You will have the advantages of your skills and savvy, but you probably won’t qualify for the ZIP-code restricted FEMA vaccination sites that are specifically aimed at the city’s vulnerable communities. All of which is to say that your commendable concern for justice doesn’t mean you should reject the umbrella on offer.