What Happens If You Miss Your 2nd COVID-19 Shot? Here's What to Do—and Why It's Important to Get Both Doses

While most Americans who got their first dose of the Pfizer or Moderna COVID-19 vaccines received their second, many have missed the second recommended shot. Here's what to know if you're one of them.

While most people who received their first dose of the Pfizer or Moderna COVID-19 vaccines also received the second—95.6% among all two-dose recipients as of April 2021—the Centers for Disease Control and Prevention (CDC) said that there were still millions of people who avoided getting their second dose (the first two shots are referred to as the primary vaccine series).

There were multiple reasons for this. According to a July 2021 study published in the New England Journal of Medicine, researchers found that people were simply confused regarding the effectiveness of needing a second dose of the vaccine (they thought that one dose should do it). People were also confused about the timing of the second dose, according to this same study. Researchers stated that while most (85%) vaccinated people polled recalled being told that they needed a second dose, just 54% recalled being told that protection was strongest after the second dose. Researchers felt that the combination of confusion around needing a second dose, as well as the timing of it probably contributed to many not going for their second shot—or being late getting it.

In a UC Davis Health article, the authors stated that some people also feared the side effects of the second shot, such as flu-like symptoms, including fatigue, muscle aches, headache, and fever. This was enough to prevent some people from going for their second jab. Here's what you need to know about missing that important second shot.

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What Happens if I Miss My Second Shot?

One shot of the Pfizer or Moderna vaccine does give you some protection from COVID-19, but the risk of getting it is lowest if you get both shots. The CDC confirmed that two doses are better than one, with a study of almost 4,000 healthcare personnel, first responders, and front-line workers between December 14, 2020, and March 13, 2021, finding that one dose of the Pfizer or Moderna vaccine conferred 80% protection vs. 90% two weeks after the second dose.

Plus, the protection from one shot may not last as long as the protection from both shots, particularly against some of the virus variants, Ahmad Kamal, MD, MSc, clinical associate professor of medicine at Stanford University School of Medicine, told Health. "This is because a different type of immune response is stimulated by the second shot," explained Dr. Kamal.

And remember: Even after your second dose of the Pfizer or Moderna vaccine, you're not fully protected from COVID-19 until two weeks after that, Purvi Parikh, MD, who specializes in infectious disease allergy and immunology at NYU Langone Health, told Health.

What if I'm Late Getting My Second Shot?

Some people might simply forget to go for their second shot. In this case, get it as soon as you can, advised Dr. Parikh. "You'll get the same benefit from both shots, but you should get it ASAP, so you don't get sick between doses," said Dr. Parikh.

The recommended vaccine schedule is based on the clinical trials that initially led to emergency use authorization (EUA). "It's not possible to determine whether delaying the second dose would impact the extent of the immune response since other dosing schedules were not studied," infectious disease specialist Leonard Krilov, MD, from NYU Langone Health in Long Island, told Health. "That said, an interval up to 90 or 120 days between doses would probably still be effective, and even if it is longer, the second dose should be given."

What if My Pharmacy Has Run Out of Shots?

It's best to get both shots of your primary series of the Pfizer or Moderna vaccine from the same location because your COVID-19 vaccination records will be available there. But if your provider runs out of doses, nothing is stopping you from going elsewhere. It's a good idea to call ahead to check that they have the right vaccine since the CDC recommends that the second shot in your primary series be the same brand (Pfizer or Moderna) as your first shot.

It's also a good idea to have your vaccine card with you as it, too, has all the information about your first dose. If you've lost or misplaced your card, the provider can look you up in your state's database, but this may create further delay, said Dr. Kamal.

Even though it may be the preferred and most convenient way to get your second dose from the same vaccine provider as your first, it is not required that you do so. Many of the scheduling websites include questions to identify which dose of which vaccine you are seeking as part of making your appointment. "I know a lot of people who have received their two doses of vaccine from two different vaccine providers," Richard Seidman, MD, MPH, Chief Medical Officer of L.A. Care Health Plan, the largest publicly operated health plan in the country, told Health.

What if I Only Want One Shot?

Listen, no one likes getting shots—and if you're insistent on only having to get stuck once for your primary vaccine series, there's a simple solution: Seek a provider who gives the single-shot Johnson & Johnson (aka Janssen) vaccine.

Though the Johnson & Johnson COVID-19 vaccine underwent a recommended 10-day pause in April 2021 due to several reports of a rare and severe type of blood clot seen in patients—mainly women—who had been recently inoculated, the US Food and Drug Administration (FDA) and CDC lifted that pause after careful review, giving the OK to providers to resume doses.

Since the April 2021 pause was lifted, both the CDC and FDA maintain that the Johnson & Johnson vaccine is safe and effective in preventing COVID-19 and that the chance of developing the rare type of blood clot—which providers are referring to as thrombosis-thrombocytopenia syndrome (TTS)—is very low.

Regardless of which brand you chose for your primary vaccine series, the CDC recommends a booster dose for most people for all vaccine brands, including the Johnson & Johnson vaccine (so much for just that one jab). Of note: As of April 2022, while the CDC recommends that your primary vaccine series be the same brand, it's OK to use a different brand for your booster shot. They also recommend either the Pfizer or Moderna shot be given for the Johnson & Johnson booster shot for most people.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.

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