What to Know About Getting a COVID-19 Booster Shot

The Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) have now authorized and recommended COVID-19 booster shots for everyone age 12 and older.

Any adult 18 and older can get a booster if they received:

• Either the Pfizer/BioNTech or Moderna mRNA vaccine and completed their primary series at least five months ago
• The Johnson & Johnson single-dose shot at least two months ago

Additionally, adolescents ages 12 to 17 can get the Pfizer/BioNTech booster at least five months after completing the initial vaccination series.

The CDC cited data from small clinical trials that showed that while vaccines continue to protect against severe disease and hospitalization, their effectiveness at preventing COVID-19 infection appears to wane over time. Furthermore, a clinical trial of the Pfizer/BioNTech’s COVID-19 vaccine booster showed that it is effective in protecting against COVID-19, indicating that a booster dose may result in increased protection compared to just having the initial vaccination series.

“The CDC and FDA made their decisions based on data that showed that booster shots are safe and effective for the general adult population,” says Dr. Marcus R. Pereira, medical director of the Transplant Infectious Diseases Program at NewYork-Presbyterian/Columbia University Irving Medical Center and assistant clinical professor of medicine in the Division of Infectious Diseases at Columbia University Vagelos College of Physicians and Surgeons. “The data showed an increase in the immune response after a booster shot.”

Health Matters spoke with Dr. Pereira about the latest guidance and data on booster shots.

What have the FDA and CDC decided about COVID-19 booster shots and why?

Scientists from the FDA and CDC have closely monitored data and confirmed that vaccine protection may decrease over time. For example, studies in the United States have found that among essential workers, vaccine effectiveness against infection waned in July, though severe disease remained rare.

For this reason and because of the rise of the more contagious Delta and Omicron variants, a booster shot is now recommended for anyone over the age of 12.

The eligibility criteria has changed to make the guidance less confusing. They’re telling the general public, absolutely get a booster. And the time to do it is now, more than ever.

Are booster shots safe?

Yes, booster shots are proven to be safe. Pfizer released a study of 10,000 participants in which half of them received a booster dose and half a placebo. In terms of safety, they found no new adverse events, meaning it was consistent with what has been seen in previous studies. For those concerned about myocarditis or pericarditis, inflammation of the heart muscle or the outer lining of the heart, no cases of either were observed. In fact, the placebo group had more serious adverse events than the booster group.

In addition, the CDC found that reactions from the third dose were very similar to those after the second dose, stating that there are “no unexpected patterns of adverse reactions” and they will continue to monitor the boosters’ safety. The benefit outweighs any risks of receiving either the Pfizer or the Moderna booster dose.

Are booster shots effective?

The booster shots are not only safe, they are also shown to be very effective in boosting one’s immunity to COVID-19. In the Pfizer study, they found that the relative vaccine efficacy after the booster was more than 95%, which restores the original vaccine efficacy before immunity waned.

Moderna is still accumulating final data, but since Moderna has been shown to produce a good amount of neutralizing antibodies and total antibodies, we expect the efficacy to be on par with the Pfizer results.

It should be noted that the Moderna booster is only half the original dose. This is because the initial two doses of the Moderna vaccine were much higher comparatively speaking than the Pfizer, so individuals need only half a dose for boosting.

“They’re telling the general public, absolutely get a booster. And the time to do it is now, more than ever. ”

— Dr. Marcus Pereira

How well does a booster shot protect people from Omicron?

In separate laboratory studies, both Pfizer and Moderna found that their vaccines have decreased protection against the Omicron variants but this protection seems to be restored after booster shots. Pfizer said its booster increased the antibody titers by 25-fold. Moderna found that its booster dose of 50 micrograms increased the level of antibodies by roughly 37-fold. Because these are based on laboratory tests, it doesn’t show the body’s full immune response, but both mRNA boosters do appear to provide protection from Omicron. Therefore, it is really important for everyone eligible to get their booster shots.

If you had COVID-19 and were fully vaccinated, do you still need to get a booster?

Pfizer did study those who had prior COVID infection, and the data suggests that a booster dose is protective for that population and certainly not harmful. The combination of prior COVID-19 infection and getting the vaccines seems particularly powerful against reinfection with the SARS-CoV2 virus.

Are there any side effects to the booster?

Pain at the injection site and headaches were commonly reported side effects, but the booster dose has been shown to have a lower likelihood of side effects than the second dose.

The CDC has been monitoring injection site reactions and systemic reactions (fatigue, fever, body aches) as well as health impacts, such as the ability to work or perform daily activities. In terms of these factors, the reactions from the booster appear to be less disruptive than the reactions experienced from the second dose.

Can you mix and match vaccines?

The FDA and CDC now allow for a mix-and-match approach for booster doses. That means that those who are eligible to receive a booster shot have the option of getting any of the approved vaccines. Data show that this is safe and effective and, in some cases, particularly in the case of the J&J vaccine, mixing and matching elicits a stronger immune response.

The National Institutes of Health released a study on mixing and matching that looked at antibody data. It found that the mRNA vaccines resulted in higher antibody titers in the first 28 days after the boost. If you were to really split hairs, getting a Moderna booster looks to produce slightly better antibodies of the three, but not by much compared to Pfizer — it’s almost tied. But if I got the Johnson & Johnson, I’d choose a Moderna or Pfizer booster.

Also, remember this data is based on antibodies, so what it means in the real world is hard to know. It is up to each individual to determine which type of vaccine to get as a booster shot, so I’d recommend speaking to your doctor for more specific guidance.