An FDA advisory panel will meet Friday to determine what type of booster shot is best for people who received the Johnson & Johnson vaccine

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A medical professional giving a vaccine shot
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People who received Johnson & Johnson's single-dose COVID-19 vaccine may be better off getting a booster shot of Pfizer or Moderna's vaccine rather than a second dose, according to data reviewed by the Food and Drug Administration.

The FDA went through two studies — one from Johnson & Johnson, which has been testing the effectiveness of a second dose of their vaccine and another that looked at following the Johnson & Johnson vaccine with a booster shot of Pfizer or Moderna, which are mRNA vaccines that use a different delivery system to create antibodies that protect against COVID-19.

While a second dose of Johnson & Johnson did improve the immune response among people who received the vaccine, the other study, which has not yet been published, found that a booster shot of Moderna led to the biggest increase in antibodies, a 76-fold improvement. The Pfizer vaccine added a 35-fold boost in antibodies, and a second Johnson & Johnson dose just 4-fold.  

The researchers, from the National Institutes of Health, said though that there are limitations to their study — it was small and the follow-up period was short, plus they did not look at whether any of the participants got infected during the study.

An expert advisory panel will meet on Friday to discuss the data and determine if they will recommend a booster shot of any kind for Johnson & Johnson recipients, and will also go over a request from Moderna to approve third doses of their vaccine. The FDA and Centers for Disease Control have already approved a booster shot for Pfizer recipients over 65 years old, those who are immunocompromised and people with high-risk jobs.

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Current data shows that the single-dose Johnson & Johnson vaccine is 56% effective in preventing moderate or severe COVID-19 illness, compared to Pfizer or Moderna's vaccines, which are more than 90% effective. A second dose of Johnson & Johnson brings the vaccine up to 75% effectiveness against any illness and 100% effective against severe disease.

The majority of Americans, around 103,600,000, have received Pfizer's vaccine, while more than 69,250,000 got Moderna. Just under 15,000,000 Americans received Johnson & Johnson, though the vaccine's rollout was hampered by temporary pauses in inoculations as the CDC verified that it was safe for use, and a manufacturing mix-up that led the company to throw out 15 million doses.

As of Oct. 14, just over half of Americans, 56.6%, are fully vaccinated against COVID-19 and 65.6% have received at least one dose. Of the Americans eligible to get vaccinated, those aged 12 and up, 66.2% are fully vaccinated and 76.7% have received at least one dose.

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