Nurse Keith Grant got his second dose of Pfizer's COVID-19 vaccine on schedule from registered nurse Valerie Massaro in January at the Hartford Convention Center — 21 days after his first immunization.

Nurse Keith Grant got his second dose of Pfizer's COVID-19 vaccine on schedule from registered nurse Valerie Massaro in January at the Hartford Convention Center — 21 days after his first immunization. / AFP via Getty Images

COVID-19 vaccines are akin to liquid gold these days. As more people become eligible, the demand continues to outstrip current supply. And while states aim to manage their weekly allotments of the Pfizer and Moderna vaccines to ensure there are enough shots for second doses, there are scattered reports of snafus and postponed appointments.

In Connecticut, as officials have sorted out scheduling system glitches, the Torrington Area Health District, in the state's northwest corner, scrambled to ramp up its capacity to administer shots to residents who struggled to get second dose appointments. In California, several mass vaccination sites, including Dodger Stadium in Los Angeles, have faced temporary closures as they await their weekly shipment of doses. In Princeton, N.J., some seniors have been confused about how to secure second dose appointments after municipal vaccination centers halted operations due to supply shortages.

Though supplies are expected to increase, "it does seem that some individuals who need that second dose appointment are finding challenges" for various reasons, says Jason Schwartz of Yale University, who is tracking the rollout across the U.S. In some places, people in the second shot queue are "competing with the increasing number of individuals who are now eligible and signing up for their first dose appointments," Schwartz says.

In theory, this should not happen because vaccine providers should be receiving matched doses, explains Dr. Marc Boom, CEO of Houston Methodist, part of the Texas Medical Center. "Every Monday we receive our first dose allocations and every Wednesday we get a [shipment] with our second dose [allocations]," Boom says. "So far, that has worked extremely well" at his hospital system, with no interruptions, he adds.

Still, as thousands of new providers administer shots, and multiple distribution channels open up, Schwartz says we should probably continue to expect some glitches in the coming weeks. Though the Biden administration has purchased enough vaccine supplies to vaccinate all Americans, it will take months for those vaccines to be manufactured and delivered.

So, what can you do to maximize the likelihood you get your second dose on time? And what if the site where you're scheduled to receive that second shot temporarily runs out of vaccine? Also, what's the Centers for Disease Control and Prevention's new guidance on how to stay safe after being fully vaccinated? We have some answers:

Before you leave your first appointment, schedule your second shot

After getting your first shot, you'll likely be asked to wait in an observation area for 15 to 30 minutes. During that period, some vaccination sites will help you make your next appointment.

"States are certainly encouraging providers ... to schedule [people] for that second dose at that time," Schwartz says.

"When people are here in the observation area we encourage them and help them book their second appointment," explains Rodrigo Martinez of CIC Health, which is operating two vaccination sites in Massachusetts. Raise the question before you leave the vaccination site, he suggests to people in other states, and if an appointment isn't offered during that time, try to nail it down soon after you get home by scheduling it online.

Wherever you get your shot, you'll also be given a vaccination card after that first dose. "Hold onto it and keep it somewhere safe!" the CIC website advises, because you'll likely need it for your second shot appointment. Take a photo of the document with your phone so that if you lose it, you'll have a backup.

Bottom line, don't wait for someone to contact you about that second appointment. Be as proactive as possible.

There's wiggle room to delay the second shot if necessary

If you've received the Moderna vaccine, ideally your second shot should be given 28 days after your first one. If you get the Pfizer vaccine, the second dose should be given 21 days after the first. But what if you can't make your second appointment due to a scheduling conflict or transportation issue? Or what if the vaccination site runs out of doses on the day you're scheduled?

In a pinch, you can safely delay the second dose up to 42 days, according to the CDC. In clinical trials, vaccine-makers focused on "the shortest reasonable time to give a [second-dose] booster," explains Dr. Gabor Kellen of Johns Hopkins University. That turned out to be 21 and 28 days, respectively, for the Pfizer and Moderna vaccines. But that doesn't mean that giving the second dose somewhat later "isn't just as effective for longer term immunity," he says. The CDC guidance states that the second dose should be administered as close to the recommended interval as possible, and Kellen says that's what providers are aiming for, but he says this wiggle room makes sense.

And one more thing to remember: The Moderna and Pfizer vaccines are not designed to be interchangeable. So if your first shot is the Pfizer vaccine, your second dose should be Pfizer, too, the CDC says, except under rare, "exceptional circumstances." This is another reason to bring your vaccination card with you (or a photo of it) when you show up for your second appointment. The card specifies which vaccine you received.

Why you still need to wear a mask and take other precautions

Hopefully, you'll leave your second dose appointment feeling safer. But remember that it likely takes a couple of weeks after the second dose to reach the strongest level of immunity, and even after that the virus is still circulating widely; herd-immunity is still a long way off. So for now, the CDC recommends that even after you're fully vaccinated, you continue to follow current guidance for living in pandemic times, including wearing a mask, staying at least 6 feet away from others, avoiding crowds, avoiding poorly ventilated spaces, covering coughs and sneezes, and washing your hands often.

One more reason to keep up with those precautions for now: It's still possible that some people will become infected with the virus after vaccination. Even though vaccinated people are protected against symptomatic disease, there's been concern that even after the immunization a person may be able to become infected and transmit virus. Based on recent preliminary data, the risk appears to be low. Accordingly, the CDC has now updated its guidance, recommending that fully vaccinated people do not need to quarantine after exposure to someone who has COVID-19 or has recently tested positive for the coronavirus.

"I think it's a reasonable [policy]" says Dr. Francis Wilson, a physician at Yale University. "They are weighing the potential harms of quarantine (including loss of income) against the potential risk of spread." But this guidance could change again, he notes, as the CDC continues to evaluate new data and gains a better understanding of the shifting dynamics of the pandemic.

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