Which booster is best?

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Data from the CDC suggest that while Moderna’s initial two series vaccine is more effective than Pfizer’s, clinical trials of Pfizer’s booster shot indicate less adverse side effects than Moderna.

There’s a cocktail of booster shots on the market that both the Centers for Disease Control and Prevention and the Food and Drug Administration say recipients can “mix and match.”

The boosters available in the United States are from the same three pharmaceutical giants that offered vaccines: Moderna, Pfizer-BioNTech and Johnson & Johnson.

However, data indicate that each booster has a differing rate of effectiveness over time as well as timelines of administration

For instance, the CDC recommends waiting five months after getting the Pfizer vaccine to get the booster, six months if you had Moderna, and two months if you had the Johnson & Johnson vaccine.

So, which one should you get?

Not Johnson & Johnson says the CDC (although the agency claims that getting J&J’s booster is still safer than getting no booster at all).

On Dec. 16, the CDC released a statement advising against the Johnson & Johnson booster shot largely because of the blot clot side-effect unique to the vaccine, which is rare, but potentially deadly. In addition, research indicates that mRNA vaccines – like Pfizer and Moderna – are more effective against the coronavirus and its variants. According to http://www.vcuhealth.org, the J&J vaccine uses more traditional virus-based technology than the mRNA alternatives available on the market in the U.S.

“Today, CDC is endorsing updated recommendations made by the Advisory Committee on Immunization Practices (ACIP) for the prevention of COVID-19, expressing a clinical preference for individuals to receive an mRNA COVID-19 vaccine over Johnson & Johnson’s COVID-19 vaccine,” said a statement posted to the CDC’s website on Dec. 16. “ACIP’s unanimous recommendation followed a robust discussion of the latest evidence on vaccine effectiveness, vaccine safety and rare adverse events, and consideration of the U.S. vaccine supply.”

These findings were confirmed by a study published on Jan. 6 in a journal called The Cell. Researchers created a benign virus that mimicked omicron and using the blood collected from 239 vaccinated people tested the effectiveness of the various vaccine combinations against omicron, delta and the original iteration of the coronavirus.[1]

The study found that those who had the one dose Johnson & Johnson vaccine who got an mRNA booster had “substantially higher” protection against the coronavirus and its variants than those who just had the J&J vaccine. Nevertheless, those who had the J&J vaccine and the mRNA booster were not as effectively protected as those who had the mRNA vaccine and boosters.

“Our results would suggest that these recipients of Ad26.COV2.S [the J&J vaccine] may benefit from additional mRNA vaccine doses with the potential to further raise titers and broaden their neutralizing activity,” said the report.

As for which mRNA initial vaccine is best, it appears that Moderna is slightly better than Pfizer-BioNTech. According to a presentation from the CDC last November, over time, following the first two doses of the mRNA vaccines, “waning appears to be less pronounced for Moderna COVID-19 vaccine, compared to Pfizer-BioNTech COVID-19 vaccine recipients.”

The CDC’s report cited two recent studies, one conducted in North Carolina and another in Southern California, similar results were observed for both studies.

Vaccine effectiveness for Pfizer-BioNTech vaccine by time since second dose, outcome, and age

Lin (author), North Carolina surveillance (study platform), Alpha & Delta (variants studied), symptomatic disease, ≥12 years

Time Since Second Dose Vaccine Effectiveness % (95% Confidence Interval)

2 months 95 (95-95)

7 months 70 (69-71)

Vaccine effectiveness for Moderna vaccine by time since second dose, outcome, and age

Lin, North Carolina surveillance, Alpha & Delta, symptomatic disease, ≥12 years

Time Since Second Dose Vaccine Effectiveness % (95% CI)

2 months 96 (96-96)

7 months 82 (81-87)

According to the data from North Carolina (seen above), the Pfizer-BioNTech vaccine had a 95% rate of effectiveness after two months for those aged 12 and over and a 70% effectiveness rate after seven months.

Moderna’s rate was higher with a 96% rate of effectiveness after two months and an 82% rate of effectiveness after seven months. That’s 12 percentage points higher than Pfizer-BioNTech over time.

The data was the inverse for boosters.

Using clinical trial data for Pfizer and an unpublished study from Moderna, which both compared vaccinated individuals to placebo groups to determine their boosters’ effectiveness, the CDC concluded in its report that the Pfizer-BioNTech booster “is effective in preventing laboratory confirmed symptomatic SARS-CoV-2,” and while the Moderna booster trial “does not provide efficacy data,” it “demonstrates the ability to boost immune response.”

The CDC’s report also found that local and systemic adverse reactions were lower for all booster recipients than on the second dose of either Pfizer or Moderna’s primary vaccine series.

But the CDC noted that the “Moderna booster appears to be more reactogenic than [the] Pfizer-BioNTech booster, regardless of the primary series manufacturer” and that while the risk for myocarditis with Moderna’s booster is presently unknown, “accumulating evidence from multiple sources suggests a higher risk for myocarditis following Moderna compared to Pfizer-BioNTech primary series vaccination [however] Moderna[‘s] booster dose is a lower dose (50µg) than the primary series dose (100µg).’”

Myocarditis is inflammation of the middle layer of the heart wall.

And while the differences between the mRNA boosters are largely nuanced and presently under review, goodrx.com advises that although booster recipients can “mix and match.” it’s advisable to stick with the same company that provided your initial vaccine for your booster.

“[…] vaccine recommendations are complex and change frequently. With some exceptions, a safe move may be to stick with the same vaccine that you got originally,” wrote Joshua Murdock in an article for goodrx.com titled Which Is the Best COVID-19 Booster Shot: Pfizer, Moderna, or Johnson & Johnson?

Adding, “It’s also likely that researchers will conduct studies that look at how effective the same vaccine is over time. For example, it would make sense for Pfizer to see how effective their booster shot is following their own vaccine. They’d be less likely to research how effective the Moderna shot is following two doses of a Pfizer vaccine.”


[1] Weise, Elizabeth. “COVID-19 Boosters Offer ‘Potent’ Protection against Omicron, Study Says, Recommending Pfizer and Moderna.” USA TODAY, http://www.usatoday.com/story/news/health/2022/01/07/covid-boosters-pfizer-moderna-omicron/9123578002/.

Work Cited

  1. CDC’s Nov. ’21 report
  2. The Cell study
  3. Johnson & Johnson vaccine: How is it different?
  4. CDC Endorses ACIP’s Updated COVID-19 Vaccine Recommendations | CDC Online Newsroom | CDC
  5. COVID-19 boosters offer ‘potent’ protection against omicron, study says, recommending Pfizer and Moderna
  6. Which Is the Best COVID-19 Booster Shot: Pfizer, Moderna, or Johnson & Johnson?

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