Johnson & Johnson COVID-19 vax recipients see stronger response with Moderna, Pfizer boosters, study says, but notes comparison limitations

COVID-19 vaccine
An FDA advisory committee deciding whether to recommend Moderna and Johnson & Johnson COVID-19 vaccines for booster use will review data today and Friday. (Kunal Mahto/iStock/Getty Images Plus/Getty Images)

A study released on Wednesday ahead of an FDA advisory committee meeting on COVID-19 booster shots notes that Johnson & Johnson vaccine recipients may be better off receiving a second shot from Moderna or Pfizer-BioNTech.

The preprint data may factor into the ongoing FDA advisory committee meeting over today and Friday to consider whether to recommend additional doses as boosters for J&J's and Moderna's authorized vaccines.

The study, conducted by the NIH, has its limitations as it relies on antibody counts. Experts have yet to be able to equate immune response to actual protection.

The authors of the preprint paper also warn that the study has limitations from the standpoint of its timelines, as booster doses were administered between four and six months. The FDA AdComm will evaluate the performance of J&J's second shot at both 2-3 months and six-plus months after the first authorized jab.

They conclude that the data suggest that if a vaccine is approved or authorized as a booster, an immune response will be generated regardless of the primary COVID-19 vaccination regimen. The primary vaccine regimens currently on the market are a single dose of J&J's vaccine and two-dose regimens from Moderna and of Pfizer's Comirnaty. 

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In the preprint study, 458 volunteers were broken up (PDF) into three groups depending on which of the three currently authorized vaccines they originally received. Then, within each of those groups, participants were further subdivided into three more groups, with each provided one dose of the vaccines as a booster four to six months after the original vaccination.

The most significant finding was that J&J recipients who received a second shot of the Moderna or Pfizer vaccine got an antibody surge 10 to 20 times greater than those boosted with another J&J shot.

The study warns that immune response from a J&J booster could rise beyond the study period, in which antibody levels were checked after two and four weeks.

Last month, J&J revealed data from a phase 3 trial that showed a second shot of its vaccine given two months after the first provides 94% protection against symptomatic COVID-19 and 100% protection against a severe form of the disease when measured at least 14 days after the second dose. Additionally, the two doses given two months apart yielded a four- to six-fold increase in antibody levels compared to those levels after just one dose.

The recent findings also show that those who were originally inoculated with the two-dose primary series from Moderna or Pfizer saw similar immune responses with either of the mRNA vaccines. Additionally, those vaccinated exclusively with Moderna shots had slightly higher antibody counts than those who were dosed with Pfizer, either as a primary or as a booster dose.

The FDA advisers will vote on whether to recommend that Moderna and J&J can offer their shots as boosters. Last month, the FDA signed off on allowing a single dose of the Pfizer vaccine as a booster six months after the initial two doses but only for those 65 and older and adults with conditions or occupations that make them more susceptible to the virus.

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Almost immediately after its approval in February, J&J’s vaccine was paused as the FDA investigated rare cases of blood clotting that occurred alongside bleeding. The company also was plagued by a slow rollout due in part to manufacturing problems at an Emergent plant in Baltimore. 

While 235.5 million doses of Pfizer's vaccine have been administered in the United States as well as 153.2 million doses of Moderna's, only 15.2 million of J&J's vaccine have been deployed.