A booster of Moderna or Pfizer works best in those vaccinated with Johnson & Johnson

In people first vaccinated with “J&J”, antibody levels increased fourfold after a booster dose of the same vaccine, 35-fold after a booster of Pfizer, and 76-fold with Moderna.

People who have received the Covid-19 vaccine from Johnson & Johnson may benefit from receiving a booster dose of a different, messenger RNA vaccine, according to preliminary results from a US study published Wednesday, October 13. This study, funded by the National Institutes of Health (NIH), was eagerly awaited in the United States because it examines the possibility of “mixing” vaccines – that is, using a different vaccine for the dose. as a reminder that for the initial series – which is not allowed at the moment in the country.

The study was carried out on 458 adults vaccinated with one of the three remedies authorized in the United States (Pfizer, Moderna or Johnson & Johnson), for at least 12 weeks. These three groups were each divided into three new groups, to receive respectively one of the three available vaccines as a booster dose. The nine groups in total therefore consisted of about 50 people each. The researchers then analyzed the antibody levels 15 days after the injection of the booster dose.

In people first vaccinated with Johnson & Johnson, antibody levels increased by 4 times after a booster dose of the same vaccine, by 35 after a booster of Pfizer, and by 76 after a booster of Moderna. And the antibody levels of people first vaccinated with Moderna were higher each time compared to people first vaccinated with Pfizer or Johnson & Johnson, and this “Regardless of the vaccine administered for the booster dose”, notes the study. Furthermore, “No security problem has been identified” after the administration of the reminders, it is specified.

The limits of the study

The study, which has not yet been peer-reviewed, has several limitations, however. First, the booster dosage of Moderna administered was 100 micrograms, which is double what the company is actually envisioning for its booster dose. In addition, the number of participants was reduced, and the immune response could evolve over time, beyond the 15 days observed here. “It is important not to get carried away by these results”, warned on Twitter Peter Hotez, professor at Baylor College of Medicine. The results of trials on a second booster dose of “J&J” conducted by the company itself over a longer period were “Impressive”, he recalled.

The NIH study should in any case feed the discussions of a committee of experts from the United States Medicines Agency (FDA), which must study the authorization requests for a booster dose of Moderna and Johnson & Johnson , Thursday and Friday, respectively. A booster of Pfizer’s vaccine is already authorized in the country for certain categories of populations.


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