What Happens If You Skip Or Delay The Second COVID-19 Vaccine Dose?

Here's everything you need to know about not getting your second coronavirus shot on time (or at all) and how it affects immunity.

The coronavirus vaccine is a dream in this long and grueling pandemic. But the rollout has been sticky. Initially, the U.S. faced vaccine supply shortages and many people faced canceled appointments. But now, months into the nationwide vaccination effort, some people who got the Pfizer or Moderna shots are delaying or opting out of their second doses.

The New York Times reported in late April that about 8% of people who received one dose of the Pfizer or Moderna vaccines had not yet returned to get their second shot, according to Dr. Anthony Fauci.

What happens if you do that? Can you forego the second jab? Can you get it late if your second appointment got messed up or you can’t make it on the exact day?

Typically, you’ll get a second appointment if you’ve secured your first; many places will make both appointments for you at the same time. And it’s important to get both shots in order to achieve full protection from COVID-19 — unless, of course, you’re given a one-dose vaccine like Johnson and Johnson’s.

That said, there is some wiggle room. Here’s what else to know about the timing of your second coronavirus shot and what happens if you skip it:

One dose of Pfizer’s or Moderna’s vaccine isn’t as effective

Real world data shows that the Pfizer vaccine is about 80% effective against COVID-19 two weeks after you received your first dose. With both shots, the vaccine is more than 90% effective against COVID-19 and nearly perfect against severe disease and death.

Moderna’s vaccine efficacy after one dose is the same. It’s also more than 90% effective at protecting against COVID-19 after two doses and more than 95% when it comes to severe disease and death.

The stats about the efficacy of the first vaccine sound great ― and they are ― but experts stress that both doses are needed if we want to really make progress on tamping down the pandemic.

“Bottom line of my message: Get vaccinated. And if you’re having a two-dose regimen, make sure you get that second dose, too,” Fauci said in a late April press conference.

It’s OK to get the second COVID-19 shot later than scheduled — just not too late

Depending on which vaccine you’re administered, you’ll be scheduled for your second dose about 21 or 28 days after the first. But don’t panic if you can’t make it on that exact date, said Kavita Patel, a practicing internal medicine physician in Washington, D.C.

“The CDC has gone on record to state that you can safely get the second dose about 42 days out for Moderna and Pfizer ― you can also get it a couple of days earlier as well,” she said.

It’s currently unknown whether there’s a time that’s too late to take your second dose because that situation hasn’t been studied yet, Patel added. That means it’s also unclear if you have to start all over if too much time has passed after your first dose.

“For other vaccines that are multidose, we don’t necessarily start the series over. ... If it’s more than 90 days, I would imagine some might recommend restarting,” Patel said.

One shot of Pfizer's or Moderna's COVID-19 vaccine is not as effective as getting both.
FG Trade via Getty Images
One shot of Pfizer's or Moderna's COVID-19 vaccine is not as effective as getting both.

In rare cases, you may be able to get a second dose from a different manufacturer

“If people really think that there is no way to get the same manufacturer for the second dose, then the CDC has also said you can substitute a different manufacturer for that second one,” Patel said.

However, this should be considered a last-resort option. “It’s not encouraged but it would be OK ― again only if you cant find the second dose from the same manufacturer,” Patel said.

Just don’t put off getting the second dose entirely

Both Pfizer’s and Moderna’s COVID-19 vaccines require two doses to truly work. You may gain some level of protection from one shot, but the second booster is vital for complete immunity.

Even if you had side effects ― or are worried about side effects ― you should still get your second dose. Side effects are a totally normal reaction to the vaccine, and they don’t last long.

“The second shot can potentially be hard on some people,” Patel said. “I personally felt fatigue and just tired the day after, so I would recommend people try to do what they can to not overload their schedules the day after both shots.” And this isn’t a guarantee. Many people also had no side effects at all or very minimal ones.

The only time you should not get your second shot is if your doctor told you not to do so, according to the Centers for Disease Control and Prevention. This may include individuals who had severe allergic reactions to their first dose (which is rare).

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.