A critical challenge inherited by the Biden administration is managing the rollout of the COVID-19 vaccination program. In one of its singular achievements, the Trump administration successfully oversaw the development of vaccines in record time, but its planning for their widespread distribution proved inadequate, with reports of promised shipments not being delivered and other supply-chain issues.

New Hampshire itself has not been spared a rocky rollout, particularly as it moved at the end of January into its so-called Phase 1b, which opened up vaccinations to everyone over 65, and others with at least two specified risk conditions. When combined with the health-care workers, first responders and residents and staff at long-term care facilities who were previously eligible in Phase 1a, close to a third of the state’s population is now eligible.

The principal challenge is, of course, obtaining sufficient doses. When Phase 1b began, the Granite State’s weekly first-dose allocation was about 17,500. At that rate, it would take 20 weeks to administer first doses to just the estimated 350,000 residents who became eligible in Phase 1b. With public health officials projecting that anywhere from 70 to 90 percent of the nation’s population must be vaccinated to bring the coronavirus to heel, clearly ramping up supply is critical. That’s on the Biden administration, and the president has promised that 100 million vaccines will be administered within his first 100 days in office.

And already New Hampshire has seen its supply accelerated. According to data maintained by the Centers for Disease Control and Prevention, the state’s weekly allocation began increasing two weeks ago and next week will be about 22,500, a 27 percent increase in three weeks. The allocation still needs to increase much further — and the imminent availability of a third vaccine for distribution should help drive it up — but the recent step-up is a good sign for the factor most out of the state’s control.

But the factors within the state’s control — actually putting shots in arms — proved problematic as Phase 1b began, and the CDC reports the state is administering only about 63 percent of its delivered doses, a disappointing 27th among the states. Curiously for a state that prides itself on going it alone, New Hampshire opted to rely on the federal VAMS online registration system developed last year by the CDC. Why Gov. Chris Sununu’s administration chose to do so — New Hampshire is one of only nine states that did — is not clear, though a recent report by N.H. Public Radio suggests that it may have been the state’s only option because it’s the only state without a fully functioning general vaccine registry.

The VAMS system caused confusion here when Phase 1b opened up, but a common complaint of how far out first-dose appointments could be obtained may be as much a result of supply limitations as the clunkiness of the VAMS system. Fortunately, the experience in other states of the VAMS system seemingly canceling or mis-scheduling appointments has not been the principal concern. Rather, it’s been problems with scheduling second-dose appointments that have proved vexing.

Both of the available vaccines require a second dose to reach their full efficacy — ideally, 21 days after the first dose for the Pfizer-BioNTech vaccine and 28 days for the Moderna — and supply is not a concern, as the state has, each week, received a second-dose allocation equal to its first-dose allocation. Yet somehow, those getting their first dose were unable to schedule a second appointment within the recommended window, in some cases not even until 10 weeks out, causing anxiety that the first dose will prove worthless.

Gov. Sununu has apologized for the frustration this has caused and given assurance that a timely second vaccination will be available to all. Beginning this week, those receiving first doses are immediately scheduled for a second dose, and the administration has been working hard to open up new second-dose appointment slots within the recommended time frame and pledges to contact every first-dose recipient who hasn’t scheduled one. The governor also now says the state will develop its own registration system to replace VAMS. All these are welcome developments, though they do raise the question of why scheduling second doses at the first-dose appointment, opening up more second-dose appointment times and home-growing a registration system, weren’t implemented earlier.

For a vaccination program as massive as the current COVID-19 rollout, it’s not surprising all has not gone smoothly. The ramping up of supply by the Biden administration and the course-correction by the Sununu administration in managing the scheduling and other logistics offer promise that the degree of vaccination public health officials say is necessary can be achieved sooner, more efficiently and with less anxiety.